Turning off a camera will not save bandwidth for the group. It will only effect the single user's ISP bandwidth which is minimal. Everyone in a meeting is connected to the Zoom server, not a bunch of individual users. Zoom's compression algorithm compensates for the bandwidth issue. BTW, be sure to upgrade to Zoom client v.5.11.3 or later by August 6. There is a security issue Zoom has fixed with 5.11.
All that said, we switched to MS Teams (a form of Skype) and are much happier with overall performance and features.