Browser compatability

At the Jitsi call this last Monday it was stated that Jitsi now works in Firefox. I tried this and no video or audio is visible from either party in a 2 user connection.
I have my own installation on a cloud hosted machine that was fully updated Tuesday of this week.
Did the comment apply to jitsi meet app or to all versions?

Secondly as a user who is learning about installation can you direct me to any guidance about the relationship between number of callers on a single call, cpu, RAM and bandwidth?
Many thanks