Two days in with a CLC 280 here.   Using an i7-7700k that idles at 35-38c stock on an MSI board with the pump connected to the pump header and the fans to a sysfan via a splitter. Using the latest Flow Control update.
 
Frankly, I'm very confused about how to control fan speeds and reduce noise. 
 
(Short version of all this is no matter the changes made with Flow Control, fan speeds are always at or just above 50% except when CPU temps hit 60C, when they max out.)
 
1. Specs say fan speed range is 600-2200 rpms. Lowest speed I've seen here is 960, accomplished by clicking the green "Auto" on Flow Control to white (presumably this disables "Auto" -- whatever that is -- but since there are NO instructions or help screens it isn't at all clear what that does) and then manually pulling the fan slider all the way down.
 
2. Fixed minimum fan speed in Flow Control is 25%.  Twenty-five percent of 2200 is 550.   I've tried setting both CPU and coolant fan curves with all points between the fixed min and max to 25% at 40C. After a reboot, the results:  At the idle of 35-38C, fan speed varies from 1060-1200. Since both CPU and coolant temps are below 40C, why arent the fans at 550 RPMs? 
 
If I stress the CPU using that flat fan curve, fan speed does spike to 1980 (not 2200) at 60C. Speed drops to 1060-1080 after terminating the stress program and CPU temp returns to 35-38C.
 
At the moment Flow Control is showing CPU at 35C, coolant at 34C, pump speed at 2910, and Fan Speed at 1080.  "Auto" is green and both fan curves are set to 27% at 40C. 27% of 2200 is 594.
 
3. Fan noise increases dramatically as soon as I close an open instance of Flow Control. HWMonitor shows speed jumps to 1340-1500.
 
4. Also unclear on how to create/edit/delete profiles. Is the intent that the "Apply" button goes white when a change is made, and clicking that white button will save the changes in a profile?  If so, which profile? All profile numbers here are currently dimmed out.  If I left click or right click on a profile number, it goes white. 
 
The "Apply" button is usually dimmed out, sometimes it's white of its own volition, and sometimes, but not always, it changes to white after I adjust something.
 
Also unclear how to select one of multiple profiles and if that selection survives a restart.
 
5.  Disabling the CPU fan curve enables the coolant curve, and vice versa.  What if I want to disable both and control fans via BIOS? (That would be with the pump fan set to PWM here.  Setting it to DC or AUTO drop the speed to 0 and produce a "NO CPU FAN!" message on reboot.)
 
7. As reported elsewhere, the "LED Temp" option is not permanent and clicking the "OK" button appears to do nothing.
 
 8.  If Flow Control's "Run at StartUp" option is enabled and I open a window of the running instance via the Task Bar and then close it, the entire app terminates completely and fan speed jumps.  

I’m confused about how to create a profile. Is it only the fan curve? Does it include the position of the Pump and Fan sliders? Which takes precedence, the curve or the sliders?

How is a fan curve applied? By saving a profile and reloading?

Does a profile include LED, update options, etc?

Does right clicking save a profile? Is a profile loaded automatically on startup? If so, which one?

What should be set to 100% in BIOS? Fan speed? BIOS offers PWM, DC, and AUTO selections with “Smart Fan Control” option offered for any of those three choices.

Pump speed needs to be kept at 100% if controlled via BIOS although Flow Control allows it reduced well below 100%? (I’ve seen recommendations to use the sliders to reduce fan and pump speed to the minimum to reduce noise. The fans, like all fans, are obtrusively loud over 1000 rpm.)

The board has CPUFan and PUMP headers. I’m currently using PUMP.

The fan curve percent is not the percent of the max fan speed. In Flow Control this % is the duty cycle of the PWM signal. I tested it with one of my fans because I was having similar frustrations:
 

 
You'll notice at 25% duty cycle the fan will spin at around 1000RPM. Why does Flow Control limit the lowest PWM signal to 25%? I have no idea. Best solution is to control via some other method, probably Mobo PWM fan headers.

Replace the horribly noisy EVGA fans to cheap, but reliable and efficient Arctic PWM PST fans. They are interconnectable and even with 700 rpm less max speed (1800 vs 2500) I regained the same 5000Mhz overclock with the EVGA OC Robot in my BIOS. Or if you have deep pockets, go with Noctua and their Y-splitters that come with the product. Just anything interconnectable will do.
Connect fans together and then connect the last fan to the motherboard anywhere you want. I used CPUFAN2. Then you will have complete control via BIOS over the originally horrendous piece of hardware and software you have bought.
The pump I have connected to CPUFAN1, since I have no pump header on my EVGA FTW WIFI Z490 mobo. Put that to 100% in the BIOS. I don't know if it's of any help, because I still don't have the "apply" button active in Flow Control. I had it active at one time but I don't remember or get what were the circumstances that enabled it or does it help.
The Flow Control is a piece of crap for software, and luckily you don't have to use it anymore for the fans if you do what I tell you, but I think the pump will be running on the speed you have set it on even after reboot.
Because the AIO is warranted, I have it on max setting 24/7 since the noise is just about the same on all settings and does not bother. Basically you will need the app only if you want to change the color and behaviour of the RGB EVGA-logo on the pump itself.

I have tried the aforementioned EVGA fans as case fans after removing them from the AIO, but there's just something wrong with the motors or the bearings - or likely: both.
The noise is just unacceptable at all speeds.
You will just have to throw them to garbage.

It is a shame, but this is the only way to live with an EVGA AIO. Replace the fans and connect them to the mobo, use the BIOS to control them, and then, and only then you will have silence and peace. You will just have to accept that in it's original state, the EVGA AIO is just crap!
The Arctic P12 or P14 PWM PST fans are optimized for radiators and sell for just about 7$ a piece. They are test winners, warranted for 5 or more years, powerful and silent and come with integrated Y-splitters in each fan. I can really recommend them! I have the 360 AIO and I only had to spend like twenty euros to do this complete overhaul, and I think this is a better choice than to try getting your money back. I think you won't get it back, since the AIO kinda works with the original setup. It's just unusable because of the noise..
Spend the 20 and your good to go with no regrets!