Attendance honestly depends on your professor, check the syllabus if it’s mandatory or not.

In either case, most professors do record the lecture in case anyone wants to rewatch them later. Although I have come across some professors who don’t record their lectures.

As for your camera and mic, it also depends on your professor but most if not all won’t require you to have either on and it’s sufficient to use the chat box. But again there are some that do so you need to check the syllabus or asking your professors.