Thanks for the award! As much as I love to talk about the structures of government, I figured I'd keep it as relevant to the question as possible. It doesn't even touch on cities with commissioners instead of a city council, mostly because I'm reasonably sure no Plan C cities currently exist in Massachusetts, despite it being an option in statute.

If any other nerds want to know more about other municipalities' forms of government, I found this listing from the MMA from a few years ago: https://www.mma.org/wp-content/uploads/2018/07/muni_forms_of_gov_2017.pdf. There have been a few changes since then (as someone mentioned elsewhere in the thread, Framingham is now a city) but it is still a good overview.