did you get KOTOR installed and working? I am fighting through trying to get it to work. I can only play in window mode, or else buttons do not work. Also not sure how to go about applying the Widescreen fix, as everything seems to be Windows-based (as well as all of the user created stuff, which is not in the Steam Workshop, unlike KOTOR2)I don't want to derail this thread at all (so tell me if I am and I will create a new thread and remove this). Steam is installed and Proton enabled. I'm currently downloading KOTOR (KOTOR 2 was already enabled for Linux) and UT 2003 to see how well the Windows to Linux runtime works.
Steam already plays Civ V and Beyond Earth on Linux. I'm taking it on faith that it works so haven't tried it yet.
Battle.net with World of Warcraft and Diablo III were a bit of a pain to install (a great Reddit post exists for what to do to prepare Manjaro for the Blizzard transplant). Both WoW and D3 are buggy enough on Windows so I'm not anticipating a seamless journey here but if either have issues on Linux I still have the ASUS laptop running Windows to fall back to.
I will say games seemed to work more flawlessly in Ubuntu, but I enjoy KDE Manjaro much more as an OS, overall.