There's currently somewhere around 68,000 games on Steam and so it's going to take a long time for Valve to check them all on Steam Deck but here's some recent picks.
I see this type of comment all the time on here. I tried switching over completely a week ago and had nothing but problems.
I went with Kubuntu after hearing success stories of gaming on Ubuntu and the great GUI of KDE. R5 5600X and 3080 Ti.
Framerate on Arma 3 was abysmal. It's mostly CPU locked so NVIDIA drivers aren't as critical. Max 30 FPS in a location I'd usually get 75+.
Lutris was unable to install the blizzard launcher. It was giving me an error about using a 64 bit version of WINE instead of 32 despite Lutris pulling the dependencies. I manually installed the supposed packages and had no option to manually select them in the installation process. Lutris automatically selected the wrong one and I gave up after that - about an hour of trying to install it.
Gaming on Linux is nowhere near ready for most people. There's just too much troubleshooting and frustration.
If you only tried two games, one of them was launcher problems on Blizzards end (fuck Blizzard), then you can't really comment on much. ArmA is notoriously CPU entensive, and it may not work well with Linux. Is it marked on Steam as Linux compatible?