International lounge access - be it QF or OW partners isn't usually a thing - specially when arriving on international flights because one usually proceeds through entry formalities at the destination and have no direct access to a lounge due to the path allowed. Yes, somewhere like SIN is an exception in that one world, but the QF arrivals policy is domestic only and you can understand why in a way. However again, most ports don't allow airside access to departures areas anyway post international arrival so it's logistically not really possible in most places imo.
Again as above, it would be possible though to, for example, arrive at say MEL or SYD on international and pop over to the domestic lounge(s) to use. At MEL this would be relatively trivial (assuming HLO or a place to store checked bags), in SYD would be more trouble than it's worth imo (same with BNE). PER could be done by walking up to T4 without too muc trouble, but again would it be worth it? perhaps for a shower and coffee I could see that.
Anyway the shadows and seat request perks are not published (as above) but usually a thing to varying degrees.
Anyway F lounge access for QF, OW and EK is a huge plus over SG, plus domestic J lounges can be a nice option there too (specially in places like MEL and PER imo).
OWE (emerald) gives extras on partners - again better lounge access, extra free bags on AS and AA, priority and seat selection to preferred seats (I know AA dropped free MCE, but still other paid "preferred" seats open up). I also think there's far more leeway and help provided for emerald's when things go south. Oh, and there are little bonuses like Flagship First entry at LAX (and I think in a couple of other locations?) of a dedicated check in experience that can include an escort to the front of the security line (which has been a huge time sAAver!).
and of course on QF, treatment during IIOPS will be better than Gold (and lower).
Now is it worth chasing for all of these (and probably others i've not thought of) things? That's a very subjective call up to individuals based on their own situations - in some cases it will be, and in others it may be a bridge too far, or not make sense with projected travel needs.