Assuming you’re making your own rotor, that’s likely the best option at this point, yes.
We used to sell the M100/M200 as standalone motors that weren’t built in to a thruster housing. We’re currently working on bringing back the M200 with some extra robustness, but it likely won’t be available again until some time next year (we have several ongoing development projects).
Not that I’m aware of. From a quick forum search of “T200 gear” / “M200 gear” the following comment seemed the most relevant, but you may find other interesting tidbits in other comments/threads