I don’t think you’ll have any issues, none that you didn’t already anyway. If you use archinstall it installs the drivers for you. Not sure about freesync as I can’t really tell the difference, but there’s a setting and it seems to do something.
Not sure if xwayland flicker (including on some games) is a thing on gnome, but on kde you’ll need the nvidia 555 beta driver to get it mostly fixed. It’s on aur but you need the flag -Syud (on paru) since the dependencies can’t seem to be resolved automatically.
About the mount points, I can only think of backing up fstab and swapping the uuids.
Highly recommend kde, although don’t get your hopes too high with hdr. It’s still not finalized so most programs don’t support it. You can run games inside gamescope to make them see the hdr support but since gamesope doesn’t support multiple windows any game with a launcher makes it crash. And when hdr is enabled the color profile is set to the built in color profile of the monitor, which for my monitor makes all the colors extremely dull and boring in comparison to no color profile.