As a generalisation, the routes operating with a 77W have more premium seating than on the 789v1 or 789v2, and so possibly better upgrade availability. The 77W usually is operating to Nth America, and seasonally to Singapore, so that would be my start point. But you can be surprised by availability also through NE Asia - for example PVG, ICN or TPE.

But mainly you’ll have to do some legwork, and make some calls to AirNZ…