The meeting itself
Google Meet
The capacity ladder is the one thing the evidence commits to per plan — 100, 150, 500, 1000 participants, 24-hour meetings on every tier, in-domain live streaming on Enterprise. Beyond that, nothing: no screen sharing, no breakout rooms, no host moderation, no word on behaviour when the connection degrades — capacity is claimed, the meeting's workings are not.
Zoom
Capacity is published per plan — 100 participants on Basic and Pro, 300 on Business, a paid add-on reaching 5,000, webinars at 500 — and breakout rooms are documented down to five roles, timers, preassignment and help requests, with waiting rooms, passcodes and authenticated-only joining enforced at the API level. What keeps this out of the top band: I found no public information on per-participant moderation detail, simulcast or adaptive bitrate under load, or what happens to the call on a constrained connection.