Chairman's Lounge
The Sydney Chairman's Lounge can be reached by walking straight ahead when you get to the top of the escalator, instead of doing a hard right and going into the Qantas Club, the Adelaide CL is on your right (with a door marked 'Private'). (incidentally the Adelaide CL is considered the worst in Australia and, unless it has been updated since the last time i was there, looks like something straight out of the 70's in terms of decor, etc)
Darwin, Hobart, Launceston etc don't have Chairman's Lounges, members have to use the normal Qantas Club facilities.
As for what goes on behind the frosted doors and how it compares to the normal QC...not much different really. You have your own top shelf, self service bar, better food and the staff come and fetch to board your flight, but apart from that it is pretty similar to the Qantas Club.
I haven't used an international OW F lounge before but I imagine that it is pretty similar fit out, facilities and food and drink as a Chairman's Lounge.