I generally divide it in my mind into the US cartoon run years, the JP cartoon (Headmasters to Zone) years, and the tail end proto-G2 years.
Then again, the US cartoon run years also do kind of have their own division, obviously by the movie, but still feel mostly like a unit due to a large amount of shared cast.
I know there's a lot of overlap and broad-ness to it, but those all feel decently distinct to me and are how I subconsciously do it. I don't have any skin in the game with the above discussion I've read, but I guess this as good a place as any to explain your own opinions if you feel those categories don't suit you. Stuff like this is often extremely variable between individuals, so I think rigid categories are mostly not useful, but that's my opinion.
Seeking the Following:
- CW Brawl
- Earthrise Runabout
- Earthrise Thrust