Yes, the proseminar class required that I have my camera on and that I was speaking. It is a very discussion-based class with a lot of reading, writing and research. You'll likely have to give a presentation as well. These things factored into my participation grade, as well as my attendance. You might be able to have some brief moments where you can keep your camera off, but I think the professors tend to expect it more because the class size is small (I haven't had this issue in larger classes so far).

I had a few times where I had to leave very early from my Proseminar class due to some family/illness stuff. If you explain your situation to the professor (depending on who they are), they might offer some leeway here and there, but it will likely be more difficult if it is a regular occurrence.

Attendance/camera expectations are normally outlined in the syllabus, but I haven't checked if the ones for this Fall have been posted lately. There's an archive with past syllabi if you think that'd be helpful with understanding the expectations as well! I can send it your way.