I’ve been on Pop_OS for 4 years and I’ve used Bazzite and Endeavor on my other computers for a few months. My only issues have been with nvidia drivers (not so much of a problem anymore) and some of the propriety hardware in my laptop being funky. I’d say, honestly, if they can handle Windows they can probably handle any mainstream distro. If all they use is Steam and a browser, anything will suffice. I’d personally lean toward Bazzite as I doubt they can break it and it comes set up for gaming already. If they game with anything outside Steam, teach them how to use Lutris. The Bazzite forums and wiki pages are also great, albeit some are a bit technical, although I doubt they’ll need it if they are very tech illiterate anyway.

I use mangohud gamemoderun __NV_PRIME_RENDER_OFFLOAD=1 __GLX_VENDOR_LIBRARY_NAME=nvidia %command% for most of my games