As I recall it is a huge lounge with seating for more than 200 pax.
The large size is I believe due to it catering also to a lot of terminal 4 AA passengers.
As I recall the lounge is infect run by Sofitel for Qantas with the excellent staff wearing Sofitel name tags
This may have changed however with the lounge having been closed for over 2 years until earlier this year
Just 1 guest I believe unless Qantas 1st - however I am not 100% certain of this.