I’d settle on the software first, then find out what their recommended specs are, if any. Also I’d look to see if they recommend a specific brand of camera and audio hardware.
That was the advice I remember my CS11 professor giving to all the noobs. “Choose tthe software first, then buy the hardware it runs on.”
That was true in 1976, still true now.
I’d call the need to see everyone on screen at once as unnecessary. You really only need to see the current speaker.
But then I remember the client is the one who sets the specs.
Edit: Hasen’t that task been solved by online web conferencing. All you need is a browser.