I probably should have mentioned that I don't have a camrea, so I cannot give you any info on how that would work. My microphone works, I have shared my desktop (on KDE Plasma), and I have shared individual tabs. I can't imagine that the camera would require anything extra to work though.
I'm using pipewire with wireplumber and didn't have to install anything specific to have this all work, so I don't have any info on if there would be any pulseaudio-specific issues.
Is steam the only program you've noticed having issues? If not then here's a scary possibility to consider: Hardware Failure
I recently had my power supply destroy my MB and SSD and there were signs that I ignored just before it all went down.
If you still have your arch install usb available then boot from that and pick the memtest86 option in the boot menu to see if your ram has any faults.