My org uses Zoom for all of our video calls. We have it setup in conference rooms ranging in size from 10 chairs to 100 chairs plus several individual offices. For the smaller rooms we're just using a standard PC/TV. For the larger ones it's critical to have a good camera/microphone system or you'll never make out people and voices. I think it also takes time to get people comfortable with remembering to look/talk at the camera when in a conference room and to sort of feel the room to know how to participate
For setup our internal IT team did the small ten person conference rooms and then they hired an AV company to come in and setup the big rooms with projectors and high-def video and fancier mics. Not sure on bandwidth as that's not my area but I know we have a lot of it and there are often several video calls going on at the same point and I've never noticed issues.
I think the biggest call I've been on had 9 different connections to it, though I know our BOG has been experimenting with bigger calls (50-100 connections). From what I've heard those have been working well, but you have to have order to start with because there's just no way 100 people can all speak at the same time. For those only a select few on are speak and they use the chat for people to raise their hands to speak and someone monitors. It's tricky.
Hope this helps.
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