There is a list somewhere of which aircraft have which engine/IFE combo, but that's fairly useless in as much as you can't tell in advance which a/c is operating your service. So it will literally be that "moment of truth" once you get on board and catch a glimpse of the IFE screen for the first time.

The slight caveat to that is that I believe all the RR engined 777's have the bigger screen, so if you can tell before you board what type of engines its got (the RR ones are smaller in diameter than the GE ones) then that might give you some sort of clue.