Does the EVGA allow the exchange of the thermal paste and even the cooler as long as the backplate and the warranty seal are not removed?

Thermal Grizzly Kryonaut is better than factory thermal paste?

Yes, EVGA allows you to change the Thermal Paste and even the Thermal Pads and Coolers.
I use TF8 or MX-4 myself.
 
And there is no "warranty seal" on the back. It is a seal to let the EVGA Tech that the card was worked on.
EVGA does sell a Hybrid Kit and the Hydro Copper Water Block so you would have to remove the current Cooler to put one of this other coolers on.
Just do not mess with the Stickers that have your Serial Number on it.
But sometime they fall off so if it does make sure you put it in a safe place, one of mine did and I put it in the Retail Box the Card came in.

Leonardohlb
Does the EVGA allow the exchange of the thermal paste and even the cooler as long as the backplate and the warranty seal are not removed?

Thermal Grizzly Kryonaut is better than factory thermal paste?

 
Yes, you're allowed to.  As long as the GPU is sent back for RMA in it's original state with the exception of the TIM, you're good to go.

Hello there,
You can open the card up to reapply thermal Paste; This will not void the warranty on the card. 
There is a sticker on the back of the card over one of the screws, this is so that we know if the card was opened if it is sent in for an RMA.
As a side note, there are a few things that can void our warranties, few examples are, removed serial or manufacturers stickers, liquid damage or physical damage.
More information here: https://www.evga.com/warranty/graphics-cards/
If you do plan to replace the cooler with a water block or a third party cooler, you will need to keep the original cooler.
In the event that the unit needs to be sent in for warranty, the unit would have to be in factory condition with all components.
Hope this helps,
Robert - EVGA
 

Yes, it is One of the Many reasons to Buy EVGA cards

One of the main reasons why I stick with Evga.

So I can change everything if I want but I need to keep everything well maintained if I need the warranty and I should send everything assembled and complete as original...

Okay, thank you so much to everyone for these wonderful answers!

But what about thermal paste the Thermal Grizzly Kryonaut is better than the original thermal paste?

I'm thinking of doing this because I have a 212x left over here.

https://www.youtube.com/watch?v=1-5WEgZhCec

Leonardohlb
So I can change everything if I want but I need to keep everything well maintained if I need the warranty and I should send everything assembled and complete as original...

Okay, thank you so much to everyone for these wonderful answers!

But what about thermal paste the Thermal Grizzly Kryonaut is better than the original thermal paste?

It might be a slight improvement but that is all up to your personal preference.  I personally like MX-4 but might venture with Grizzly down the road some day but I really like MX-4 though. lol
 

Leonardohlb
I'm thinking of doing this because I have a 212x left over here.

https://www.youtube.com/watch?v=1-5WEgZhCec

Don't think that's a great idea unless you want to experiment I guess.  All up to you as long as you don't damage the GPU.

As stated above make sure to keep the original cooler.

As for thermal paste replacement don’t expect a big difference in most cases the best thermal compound and decent is just like 2C. The cooler itself is what matters more then the compound.