Saturday when all APs but the premium AP were blocked, it was surprisingly not crowded for the beginning of summer. Main Street wasn't packed for the fireworks, just to the clock. We watched the fireworks and noticed people working their way to the Rivers of America during the fireworks.
If you need to be in the front along the river, then yes you will have to go 2/3 hours early. And don't know that will change at any time of the year whether APs are blocked or not. If you want to be in the sitting area (on the pavement, no chairs), we were able to get a spot on the pavement 1 hour before the show. But I would try for the 2nd show to get the best seat and do what Diznee Luver suggested. I don't ever think WOC will thin out the F! crowds. Might thin out the general park crowds.