On the subject of genderfluidity and shapeshifters, There has been a comment floating around in my brain for a while in search of a good parent to latch onto, and yours is the most appropriate so far, so here goes:
That episode of Deep Space Nine) when Odo finally meets another non-evil Changeling who wants him to leave Kira and run away with him instead, when Odo is forced to confront the fact that he has been presenting himself as a Cisgender man for like 99% of his entire existence without ever really questioning it, nor ever even considering that he can exist as ANYTHING (even stuff like fog, or fire) because maintaining a consistent masculine gender identity was bundled up with conforming to humanoid expectations as a whole, so much so that that expectation even extended from his Public life and into his romantic relationships, is probably my favourite episode of any Star Trek show, ever.
It always seems to get overlooked whenever anybody talks about the relative paucity of queer representation in 90's Trek, but the episode literally namedrops pride parades. The sheer amount of analysis and discourse that has yet to be drawn out of this one episode alone...I mean it has got to be worth at least a couple of pages is somebody's book. The allegory of shapeshifting for sexual and gender non-conformity is as plain as day once it clicks in your brain, like the moment a magic eye painting finally comes into focus.
ODO: Look at me, Nerys. What do you see?
KIRA: I see you.
ODO: No. No, this is just a form I've borrowed. I could just as easily be someone else or something else.
KIRA: I know that. But this is what you have always chosen to be. A man. A good and honest man. A man I fell in love with. Are you trying to tell me that he never really existed?
ODO: I don't know. I care about you more than anyone I've ever known. These last few months have been the happiest of my life. But even so, part of me wishes that Laas and I were out there right now searching for the others, existing as changelings. Because that's what I am. Not a humanoid; I'm a changeling!