I think what you can and can not do in the night will depend largely on when you go and what time the various shows (illuminations, Spectro, wishes) are performed. If there are two performances of Spectro, it might be possible to catch the early show, head over to Epcot and see Illuminations.
As far as crowds after Wishes, there are a whole lot of people trying to cram themselves onto every form of transportation after the show. My advice? Take your time, wander Main Street and do a little shopping. I try and stay in the park as late as possible, knowing that when I and the rest of the shoppers are finally ready to leave, the crowds will be much less severe than in that first 20 minutes or so after the final fireworks show of the evening has ended.
Richard