I’ve had the impression that in the Mirror Universe, it was only the humans/terrans which behaved differently. Everyone else we see seems like their usual selves (accounting for different circumstances of course).
The DS9 episodes throw a wrench in this of course, with Kira being a very different person and the oppressed terrans being sympathetic.
Voyager S1E3, “Parallax”. It didn’t make much of an impression on me as a kid, but watching again recently - and knowing the direction that the characters grow - it’s actually a pretty compelling character-based drama. And the Maqui-Federation tension is thick here.