I’m using endeavourOS with Nvidia 4090 with proprietary drivers and it works fine for most games without tinkering. For issues with Linux gaming you can check protonDB. Steam, lutris and heroic game launchers are doing wonders for a big portion of the gaming options on Linux. I wouldn’t change the 3080 with AMD if I were you.
I’m using endeavourOS with Nvidia 4090 with proprietary drivers and it works fine for most games without tinkering. For issues with Linux gaming you can check protonDB. Steam, lutris and heroic game launchers are doing wonders for a big portion of the gaming options on Linux. I wouldn’t change the 3080 with AMD if I were you.