Does it work if you launch steam through mangohud? Like:
mangohud steam-native
You would probably want to temporarily remove the per-game launch command while running it that way, for the HUD to actually show up in game (assuming it will load). But that's another approach to try, at least for troubleshooting purposes.
You can. It's pretty configurable, as camera apps go. I switched because I wasn't entirely satisfied with the stock app, and haven't been disappointed so far.