Two
One
None
This is definitely a stage 2 or 3 pokemon IMO.
Excluding legendaries, ultra beasts, and alternate forms like Megas and Wishiwashi's school, there is not a single 1 stage pokemon at or above BST 560. The highest is Snorlax at 540. As such, I think this should be eliminated altogether.
I chose to prioritize 3 stages over 2 stages because of design. If we look at the art, it's a humanoid dragon. 2 stage dragons tend to be far more draconic, walking on four legs or being hunched over, growling and looking fierce. We don't start to get more friendly humanoid dragons until 3 stage evolutions.
On top of those reasons, we aren't hurting for design space. A firework is easy to design prevos for. For example: a sparkler, into a rocket, into the firework itself. That took like 5 seconds to think of.