Do I understand correctly that you could to this with OBS on any platform, including Wayland? I'm reading many comments that make me think either many people don't know about OBS, or I'm overestimating it's abilities.
It can do that, yes, but it's a bit more work. There are several GUI hoops you'll have to run through to get that to work, and if you have to adjust it each and every time, before a meeting, then it would become burdensome. But yes, it can be done.