I switched to linux before the steam deck came out, and things were already pretty good then, but it's even better now that more folks are invested in it. Since then, I haven't come across any steam games I have major issues with - however, I still have issues getting my controller running (I don't use it often though, so I haven't really looked into that much) and on certain games I have issues if I switch windows while it's running. Generally for me, if it runs, it runs well, aside from occasional issues from needing more ram. It looks like we have similar cpu's, and you have a better graphics card and more ram than me. I can't speak for everything on your list, but I did play some civ fairly recently without any problems. Check protondb for the games you play most before making the switch - and if you're worried, check lower rated games on there for examples of issues and fixes. I suspect it would be fine for you to switch.

I couldn't get RDR2 to play, but I'm also a noob. I have a drive with windows just for playin the games I can't run in linux, and maybe I boot it once a month.

Outside the few games like valorant and destiny 2, literally everything else I've tried runs just fine on Linux. Wine/Proton has gotten really good these past 2 years. Even on Wayland, which has historically been bad for gaming things just work nowadays.