A few observations-
As far as the queue and single rider, there isn't much to see in the greenhouse area except those little mandrake plants, I wouldn't care about skipping that. But if the single rider queue skips the portrait room and Dumbledore's office, those are big things to miss.
Also, on one of my queue experiences at FJ, it did take longer than the "free" time on the lockers, and I did end up paying $3.00 I think it was to get my stuff. Was kind of pissed about that.
A tip I found after a few rides on FJ.....the scenes in front of the curved screens, where you're flying on broomsticks with Harry, I found it cooler to lean forward a bit so the top of the ride vehicle isn't in your field of view- felt more like you're really flying. The other scenes, with all the animatronics and real sets, it was better to lean back in the seat and let the ride vehicle direct what you see.