In terms of domestic access, OWS equates to Qantas FF Gold, so you get whatever they get.

Domestic you'll get access to Qantas Club lounges in SYD and CNS.

From recent experience on QF1/QF2, the transit through SIN has taken longer than anticipated and I used the lounges in SIN both ways. The QF2 transit is timed at the same time as the main bank of SIN-Oz flights and so the lounge will be busier around then. For QF1, the main bank of departures has gone, and QF1 passengers have the lounge largely to themselves.