Not clear what your question is
 
You can replace the Hybrid stock AIO cooler with a hydro Copper water block - Yes
 
Can't modify the stock AIO loop without destroying the warranty ... nor would that make any sense .. no real gain & may headaches
 
much simpler to improve air flow (placement & fans) & lower room temp with A/C

You would need a new pump, radiator, tubes.

Hydro Copper (water block) requires a custom water loop.  Some vendors make kits
 
review these threads
 
Ready to try water cooling. Where to start? Library of links-basics to expert
 
Initial cost for a custom GPU water cooling loop.
 
 

redteamgo
Ugh, really?  I can't retro fit the existing hybrid bits to the HC block?  That is sad :(

LOL! You wish buddy.
 
Good luck, you're going to need it.
 
https://www.performance-pcs.com/
 
https://www.performance-p...panels-aq-33044-d.html

redteamgo
Ugh, really?  I can't retro fit the existing hybrid bits to the HC block?  That is sad :(

Hey let me know if you're selling your 360 radiator and pump. I'm interested in buying it and testing it out on my 3080 Ti Hybrid. 

KingEngineRevUp

redteamgo
Ugh, really?  I can't retro fit the existing hybrid bits to the HC block?  That is sad :(

Hey let me know if you're selling your 360 radiator and pump. I'm interested in buying it and testing it out on my 3080 Ti Hybrid. 

I wouldn't advise him to sell it because he wouldn't be able to return his card back to factory if he needs to warranty it.

Decided to keep the kit.  Is there a premade kit by chance that I can buy to get a custom loop running for the KP HC and an intel LGA1200 ??  
 
 

Great idea thank you.  I found a build that I'd like to imitate... namely because its the only one I found with a video and a parts list for my case lol.
 
There is a parts list in the video description.  It looks like his tubing size is a bit different. So I need to get G1/4 tubes/fittings but the pump / reservoir / rads just take whatever fittings I put on right?
 
The KP HC kit recommends that you only get copper parts.  It looks like all EKWB fittings are Nickel plated and finished in various colors.  Or is it only aluminum that needs to be avoided?
 
Thanks again, I know this is remedial
 
https://www.youtube.com/watch?v=A0Cg1jr65Fk
 
 

Great thanks man
 
EKWB says the housing of their radiators is aluminum but the chambers and fittings are brass and the fins are copper.  I'm guessing That is fine as well, right?

Redteamtango,
The EK Magnitude is expensive, I'd recommend looking at the Optimus block for the CPU if possible.  It's a great option and I had both in hand to compare.  I went with the Optimus for my build plus is about a $100 cheaper too.  It will go on very similar to what the youtuber used overall.  
 
Another thing I noticed but may have missed is that the video poster did not include a drain valve.  I would recommend finding a spot to add a three way connecter and place a drain valve as it will help when you have to drain the system.  Also, because you are using a low horizontal mount res, you might want to put another 3 way connector up high where you can add a fill port to help make it easier to fill the loop.  It will help save you time and headaches since in the video the guy fills up with the PC with it on it's i/o port side.  You wont be able to access the power cord easily unless you prime the system using a secondary PSU which is what I do when I fill my system. 
 
When I'm filling my loop, the only thing with power is absolutely the pump and the PSU I saved from a pervious build that I use to power the pump which is not connect to my pc.  It just sits next to it and provides the molex plug to power the D5 pump.  
 
MDB983 is right about the aluminum.  Avoid that with copper/nickel and you should be fine. Find a fluid you are comfortable with but be aware that most fluids that look great are for show and will clog your cooling fins overtime.  Some will last longer than others, but there are a ton of videos on youtube to review and you'll have to see what is available and at what cost.  

redteamgo
Gotspeed, thanks so much for your feedback
 
I was going to use plain distilled water for the cooler.  Do the below parts work based on your thoughts?  
 
Three way splitter x 2
https://www.performance-pcs.com/water-cooling/fittings-connectors/ek-quantum-torque-splitter-3f-t-black-nickel-1.html
 
Drain valve x 2
https://www.performance-pcs.com/water-cooling/fittings-connectors/ek-quantum-torque-drain-valve-black-nickel.html
 
Thanks again
 
RTG

Redteamtango,
The 3 way port should be able to be used.  One thing though you may need to order is the male to male adapter depending on where you put the adapter.  If you use it as an in-line  then you wont need any, but if you are having come off a rad or res you may need a male to male adapter to use to connect this to the rad/res.  I used this splitter also from EK:  https://www.performance-pcs.com/water-cooling/fittings-connectors/ek-af-t-splitter-3f-g1-4-nickel-ek-af-t-3f-g14-nk.html.  To me it was cleaner for the install and where I placed it in my loop.  
 
The drain valve you showed is the same unit I am using in my system.  It has a push/pull open close design along with a thread on cap to help make sure it is closed until needed.  You could use one to fill at the top of your loop and another at the bottom to drain.  Having the fill port at the top will make it easier to fill the system but I think you may still have issues filling it and getting all the air out of the loop.  
 
There are also fill specific ports other manufacturers sell that require you to drill a hole though your case to mount the fill port, but I think the push pull EK using can be used easily.  You would just need to setup another tube like you would to drain the system.  Using a soft tube fitting, you can screw it into the EK drain port on your unscrew the cover, open the valve and it will allow you fill from that port.  It's kinda hard to explain, but you could easily use that port at the top of your loop to fill from and then keep some excess in there to help bleed the system of air. 
 
I do have to be honest though and say that I think most of the air in your system is going to get caught in your res and because it is mounted in a horizontal position, getting it out of the system may prove a bit challenging if you follow that build you linked.  Even with the fill port up high, it might not catch the air bubbles as they move through the system. 
 
I looked at the video again, and I'm not sure why the original poster of the video just didn't use a EK D5 Kenetic TBE 200 combo instead.  That way the pump and res are actually one piece and take up less space.  The D5 pump head and the res he uses are the same two pieces used in this part if I'm not mistaken.  You can brace the top of the res with foam pad/block to help balance the weight. The three 8 pin GPU power cables would then be run in front and around the pump/res combo to the opening for the cables below the GPU to get to the PSU.  You might need cable extension to make the bend and fit work though, but the poster also used cable extensions or cable mods in his build already.  Also, the original poster of the video must have a drain valve somewhere hidden near the back of the front rad as he pressure tested the loop using the EK tester which would have been connected to the loop through the drain plug.  It's just a bit hidden which it normally should be but accessible for use as well.  
 
This is a photo of my build based on the 3090 FTW3 and 5800x.  I am planning on changing out the 5800x for a 5950 that I currently have and the SL120 unifans to the new AL120 fans sometime next week.  I also have the Kingpin 3090, but I am waiting on the water block for that one.  You can see my water drain on the lower right of the photo.  
 

 
Hope this helps.  
 
 

The youtube video you posted that used your case fit the pump connected to the res under the GPU.  I would think it would fit still if it was connected as one unit instead of the two the poster did.  The only concern I could see is the GPU power cables since the poster ran them between the GPU and the res.  If you run it as one unit, it would be shorter for sure, but it would also mount higher since the poster offset the res lower than the pump.  If you try to run the GPU power cables the same way, you might have issues making the bend which is why I would run the cables under the res and to the back where the cable pass through is in the case.  If you have a 24 pin strimmer kit it would work well allowing maximum use of the LEDs.  The FL is a great option, but having that res would be also helpful to catch the air bubbles in the system.  I have a feeling mounting that res horizontal is going to make getting the air out of the system tough.  
 
Cases and builds are based on the owners views and taste.  The case you are using seems a bit small for a full power system which makes it tougher to build in.  If I may recommend keeping an eye out for a larger case that would allow you great flexibility.  The O11 is very common for open loop builds, but it's that way for a reason too.  I went a little crazy not using the easy way out with a distro-plate, but that's just me.  Also adding that darn 3rd rad was a pain that drove me nuts, but I got it to work.  It wasn't needed, but I wanted it anyway.  I know you also spent a ton of cash not only going to an open loop but recently getting your KP so keeping things in perspective for now might be good to allow your bank account to heal a bit before you start changing things again.  I am lucky and fortunate as I'm not rich, but am able to do these things because I want to.  
 
I would look at the Optimus CPU block if you have a chance.  It is a really good block and it went on well.  I ordered the EK CPU block initially but since I was going to the Optimus for the GPU I ordered one for the CPU to try and keep everything uniform.  I compared the magnitude to the Optimus one and honestly I was blown away that Optimus is able to charge as little as they compared to the EK Magnitude.  I was lucky the Magnitude block I ordered was missing parts so I was able to return it but if I had kept it I would have been spending 250 for the EK block instead of the 140 for the Optimus.  They are both great blocks, but the Optimus is just better, thicker, and the materials they used are so much better.  
 
If also can recommend, since you are going with flex tubing you wont need too much fittings other than what you planned.  Sometimes in hard tubing having a variety of fittings can help when you get stuck on a short tight bend in the build.  Since soft tubing is in your plans, those shouldn't come into play.  Just make sure your fittings can clear your fans when you have them mounted to the rads.  I went with the primchill because I like how they look and how you can secure them.  The bad part was they the footprint of the base was a bit larger which required me to use extensions since the the fitting wouldn't clear the fans I used.  I bought a ton of fittings and extensions for my build, but I have them in case I need them for another in the future.