re: nautilus i am definitely in the camp that caliborn is transmasc and callie is transfem because they dont really have one gender until one of them dominates. any wish to have more control and autonomy over the body can manifest as a desire to present more heavily in one way or another. i dont think caliborn would consider himself transgender, but i definitely think it fits well for callie.

i love the idea of callie moving more towards being nonbinary and she/they after she gets a few years to have her body be fully hers and present the way that they fully want to. she ends up in a much more supportive, loving situation and reexamines herself and how she wants to be in the process. i really enjoy that and i personally find it very relatable. i think it especially does make sense when you consider how strongly she had to argue and advocate for her own gender growing up. when she isnt constantly fighting to be recognized and respected and loved she gets a space to experiment more with what feels best for her.

also i think it/its or other neopronouns would do callie well but thats just my two cents lol