Been running Arch exclusively on my gaming rig for 3 months, now, with no issue. Thanks to Proton, the only blocker is games that use anti-cheat solutions that don't work properly. Everything that's relied on VAC or EAC work fine, though.
This is my third attempt at making this move on my gaming rig. The first try was back in 2016. The second was in 2018. This time, I think I'm here to stay. The Steam Deck's success was the final ingredient.
Confirmed, been playing Apex since not long after the Steam Deck released. Pretty sure the devs will never fix R6S, though.