The Poly beach has historically been a good spot. They bring the water pageant boats out as a unique part of the show you don't get in the park. But with the construction there, not so sure how it will be this year.
Yes, the fireworks are traditionally special for FOJ and NYE... they shoot the show from behind the castle as normal as well as a mirrored and nearly identical show from an island in Seven Seas Lagoon. The finale includes launch points completely encircling MK. Patriotic music instead of Wishes soundtrack.
If you are not interested in dealing with the traffic or crowds, a lot of locals watch from the neighborhood streets off of Reams Rd behind Magic Kingdom. You won't get the soundtrack or the "experience" but you will see plenty of the bigger fireworks.