I finished my upgrade and with the i9 10900k/EVGA Z490 Dark KP and Quadro RTX 4000 im using Windows 2004 build 19041.572 completely comfortably where as on my older hardware it felt grainy/strainy, not only can i use it, this is more comfortable than my Windows 7/Quadro K4200 setup, but this might be because im using a 4K monitor and Windows 10 handling font scaling better or something, not completely sure. I havent tested the RTX A4000 card since im a bit nervous it could sabotage the setup, so i ordered another NVMe SSD to clone the existing setup to that drive and swap in the A4000. I think you are 100% onto something though about the poor compatibility of devices, i think my X79 motherboard was just too old.
I also noticed a huge increase in audio quality after i switched to the new Z490 motherboard through my Schiit Modi Multibit USB DAC which has a iFI Defender isolating the 5v line away from the motherboards USB power into a Allo Shanti linear power supply, because im isolating the 5v line, it shouldnt have improved/changed the audio quality but it did. On my X79 board if i ever plugged in a microphone to the 3.5mm jack on the back, it would emit a ton of electrical noise and people on discord would always complain about the noise, so maybe some motherboards have poor separation of traces/components and can suffer from noise and maybe newer graphics cards are more sensitive to this as well, just like audio equipment and TV's/Monitors.
Old Setup: EVGA X79 FTW | Xeon E5-2690 | Quadro K4200&Quadro RTX 4000 | Dell UP2720Q True 10bit monitor. (unusable with new RTX A4000 and previously Windows 10 2004)
New Setup: EVGA Z490 Dark KP | I9 10900K | Quadro RTX 4000 | Dell UP2720Q True 10bit monitor. (Now usable with Windows 10 2004). (Will test with RTX A4000 soon)