I personally wouldn't dedicate too much time staking out a location. I'm in the minority because I absolutely loved Harmonious....viewing Epcot Forever after Harmonious felt like a bit of a letdown...this is also the 3rd return of the show and I've seen it multiple times so maybe I'm just tired of it.
You also don't need to be against the rail to view the show, all the action is in the skies. You should be able to find a decent spot 15 minutes prior! Fireworks are still magical so worth checking out, just don't stress about finding the perfect spot.