@Kfox
To address some of these points, I'd like to share my perspective as a binary trans person. I can't say I understand nonbinary identities, but at least for binary identities, we usually
do identify with the SEX characteristics of our target sex, rather than just the gender identity.
When I was a kid, barely acquainted with gender roles, I still knew I wanted a penis. I thought I was a boy and didn't underneath why I didn't have one. I didn't understand why I got in trouble when I went into the boy's bathroom. Etc.
Going through puberty, I had massive dysphoria about my female parts themselves, and massive dissatisfaction about not having a penis, not having facial hair, etc. In all of my dreams, my brain depicted me as a male. I even had phantom limb sensations where I would feel I had a penis even though I didn't, similarly to how a amputated person still has sensations of their missing limb.
I didn't just have dissatisfaction about not fitting into a social role of "man", I LITERALLY felt a disconnect between my brain and my physical
sex ... not gender.
And I do not get gender roles, gender, and sex confused these days.
Now that I am fully transitioned and have the things I wish I was born with (besides my chromosomes, but I can't see those, and no one else can, either, so it doesn't really bother me), I feel perfectly comfortable with my partner dressing me up or putting nail polish on me. I don't quail when I enjoy stereotypically feminine hobbies. On Halloween, I even put on a woman's bunny lingerie set along with all of my cisgender male friends, because it's just a fun time to twist gender roles, and I am, in my view, male enough. No one could tell that I was born female, even wearing that. Because I am as close to male now as one can get... and thats what I care about.
To me, nothing about the hobbies I enjoy or clothes I'm willing to wear determine my identity. I don't identify with male stereotypes, I identify with the male body. Being a tomboy isn't what I needed, being as close to a biological MALE is what I needed. I didn't need to wear a masculine outfit, or drive a pickup truck... I needed a penis and balls.
That's a lot of private information, I know, but I hope this made sense about why trans people don't necessarily fall for gender roles as much as many of us identify with a biological sex.
For nonbinary people, though, it might be different.