As far as I know, only the kernel module was open sourced and in doing that Nvidia moved a lot of stuff from the driver, to the firmware/software part of their stack instead. So you would still need those, which are not open.
OBS can capture wayland output just fine. At least in recent versions 29.X for sure. I don’t know how the Debian/Raspberry Pi OS repositories updates them. Hopefully they have a newer version these days.
I’ve had no issues saving to same folder as source when doing batch transcoding queues on Arch Linux. As long as the input and output files does not have the same filename it’s fine.
The couple of apps I use through flatpak has not had any issues as far as I can tell. Other than maybe being a little slow to get pushed to the newest version.
It’s pretty new. Has wayland and pipewire. You can just enable a checkmark in the installer to install codecs. Uses Gnome, so a non-Windows like workflow. Pretty sure Eduroam would work there, as many schools use Ubuntu by default.