To tell you the truth, I think crowds at SW are much larger this year than in all years past. Would expect it to be crowded on Labor Day Weekend. That said crowded means a totally different thing than at Disney parks. At Disney you can only get so many people on the rides at a time.so there are hour waits unless you can get a fast pass. Then sometimes the fast pass you get at 9AM isn't good until 8PM. LOL We don't always stay that long in one park.
SW is huge stadiums for 4 of the shows. I know SW advises getting to the stadiums 35 to 40 minutes ahead, but that is just a waste of your time. We never stand in a line to get into any of the stadium shows. We don't want splash zone though. Any seat is OK with us. We usually arrive about 15 minutes ahead of time to find a seat. They announce when a stadium is full over the PA so just do something else if we can't get in. We love the mime so do try to get to Clyde and Semore show early, though.
Plan any meals at off times because between 11:30 and 2 PM lines for food can be quite long. A lot of people tend to arrive early and leave around 5 so after 5 the parks almost seem empty compared to earlier. Shows are not crowded in the evening. One exception is for Mystify. Try to get your spot early for that, but if watching the last Shamu show before it just walk to the other side of the lake and find the best spot you can. .