Well, "just works" depends on how you define it too. But yeah, most of the "basic" stuff just works. But I will not rule out the possibility of unsupported HW just because I have my fair share of it too. For example, I'd say a keyboard is working if they are able to be used as an input device. Even without the customization or sleep, or wake from sleep. Granted, the issue being unrecognized or not working at all is very much borked tho. Hence why I request the details of the mouse itself.
Now you mention degraded performance and glitches. Yes, I do know that. But as I said, my statement regarding the wrong driver usually entails a lot more dramatic bug than a stutter on only known 2 games. Further investigations are needed to correctly decide if it is the driver or not since we know that a compatibility layer is also playing a part here. It is also why I suggest searching the protondb to check the current support for the game. Linux gaming, as good as it is now, is not perfect yet.