I've got 5 of the CLC 280 AIO's installed.  Three of them are installed horizontally in Corsair 750D cases and are cooling Ryzen systems (2700X, 3800X and a 3900X).  The fans run at ~1080 rpm when idle and ramp up as needed.  I have two of the coolers installed vertically in Corsair 600C cases on older Intel systems (4790K and 2600K).  The fans run at ~1080 when idle and ramp up as needed.
 
The problem I have is the 600C systems are sitting on desks where the fan noise is very annoying.  I've watched the latest EVGA YouTube video and it explains everything about the software and shows the fan speed at ~1080 rpm @ 25% of max!  What am I missing.  I don't need or want the fans running @ ~1080 rpm on systems that are used for general browsing and e-mails etc.  I know I can connect the fans to the MB and try to control them at a lower speed and I know I can replace the EVGA fans with a couple of Noctua NF-A14 fans which I have done on one system and the EVGA software runs them at ~500 rpm when the system is idle.  Absolute total quiet!
 
Is there some information somewhere showing how to get the stock fans to run at less than 1080 rpm using the EVGA Flow Control software?

Almost positive there's no way.
 
But maybe you can cobble something together using the Low-Noise Adapter (L.N.A.) and the 4-Pin Y-Cable that comes with NF-A14 fans (if you're not already using them in another system) to use on the stock EVGA cooler fans..Should probably work nicely..Only one way to find out.
 
Been thinking about trying that with my Corsair cooler fans, using the L.N.A. and the 4-Pin Y-Cable that came with my NF-P12 case fans..The thing sounds like a vacuum cleaner at 100% fan speed