The limited fireworks during this show is due to the air quality regulations in China. It's worth getting in a position where you can see the projections and fountains if you want the full experience.
I've just got back from my second trip to SDL. The first night I watched from a spot that I'd found on my previous trip over near Dumbo. It was a nice easy spot to get to, on a little part of the walkway that jutted out over a pond, which had previously given me some nice fireworks reflections. Unfortunately with the rain that night, I didn't get any reflections. It's a reasonable spot to see the projections and the fireworks, but you don't see any of the fountains or water screens at the bottom of the castle.
The second night the park was so empty with the awful weather, I just walked right up to the viewing area about 15 minutes prior to the show and found a spot close to the front right on a rail but a little to the side. It was pretty much an unobstructed view of everything that was on offer, but obviously being off to the side, I didn't get the symmetry with the fireworks. I was more than happy with the spot though both for viewing and photography purposes.
The third night I did a bit of experimenting and actually watched from over the lagoon in Treasure Cove. There was a little spot by the walkthrough Pirate Ship that had a perfect unobstructed view of the castle and being a beautiful still night, some lovely reflections in the lagoon. There was also a nice bit of railing I could rest my camera on for long exposure shots of the fireworks. Being more of a projection based show, I did miss much of it from this position, but I am absolutely thrilled with my fireworks shots. Another thing to note if you plan to watch the show from anywhere other than in front of the castle (I did also consider watching from the Tomorrowland Terrace if it was raining again, as it would be completely undercover but still have a good view of the castle), is that the park is technically closed once the show begins. About halfway through the show, I was approached by a CM and asked to move on. I just kind of procrastinated moving, and eventually they allowed me to stay until the end of the show, but it would probably depend on the CM that you get.
I'll upload my favourite photo from each location when I've gone through them to give you more of an idea of what you can expect.