Did you try with C3? It has a better spritesheeting engine. Again though, there's still no evidence this is actively causing any performance issues. Each individual draw call as a tiny overhead.
Avoiding texture swaps is really hard and makes potentially worse tradeoffs. For example the ultimate way to avoid texture changes is to place absolutely everything on to one single giant spritesheet, so there is only one texture which never needs to be changed. However that reverses the benefits of layout-by-layout loading and guarantees that your game will use the maximum amount of memory at all times, which is wasteful and can cause many games to crash on some devices. Then there's the maximum texture size, so sometimes you have to spill over to another texture.
So there is no evidence this is actually too slow, and "fixing" it could easily make things a lot worse.
I'd be happy to try in C3, as I did notice that it bundle even art from other sprites in the same sprite maps. But my project is currently stuck in C2 because of plugin dependencies (photon cloud, and raytracer). Would It be possible to have an option in export for C2/C3 to manually set a target sprite map size? That way we could have a little bit more control and reducing number of sprite maps, and swapping/draws?
What's the current maximum?
So would you recommend me trying to bundle most/all of my artwork into the same sprite in C2 for now, or sprite maps as that seems to be the only thing I could do so far to control it somewhat? fewer sprites/swaps/draws seems to equal a better performance especially on mobile.