Let's talk Synchro. Although I don't think that "Evolution" is the right term for it, it's just a form.
Beware, the following are major plot spoilers:
Kukui studies moves, we know that. He's been doing that for years and continues to do so when we meet him.
What we don't know is that he knows that certain Pokémon have...potential, let's put it that way. Z-Moves require Z-Stones to get activated, but in his career he has seen various iterations of Pokémon performing one withouth the need of a stone. I'm talking, of course, about the starters. And Rockruff's evo.
So he keeps a Rockruff to study for himself (and the bracelet is based on Rockruff collar, if you didn't notice) and gives out Rowlet, Litten and Popplio to young trainers in order to gain information and empiric proofs.
The Synchronization manifests itself just like in Ash's Greninja, so minor changes in the general look to match the trainers it bonds with.
So yes, you'll get multiple version of starters, which are based on your look (see attached image for example). Have you wondered why all the final evos are sort of humanoid and have big tufts of fur/feathers on their face?
Of course they'll be able to perform a special Z-Move, just like the big Water Shuriken used Ash Greninja or the big Z beam from 100% Zygarde, and they won't need the stone at all.
It all links back to Azoth, since the starters+Popplio represent the main 4 ingredients of Alchemy (or something along those lines).
