All of the above are correct. You can go for four or five days and accomplish a lot without FP's, especially the shows. Of course, a lot depends on when you go. If its a busy period, you'll get a lot less done.
I guess my question would be why not take advantage of the FP's? Even if you're someone that doesn't decide which park they're going to until the day before or that morning, you can still set up FP's for many attractions. Maybe not the real big ones (like TSM, Soarin'), but there should still be some available. Worst case, set them up and just not use them if you're in the wrong place at the wrong time.