The corset question is really presumptuous, so I’m not really sure if you are just ignorant or if you’re feigning ignorance, but I find enough of your other questions interesting that I’ll answer a few of them.
“What are some of the ways nonbinary people experience dysphoria and is it possible to separate your experience of your physical body from your sense of gender identity, if it rejects a binary, socialized expression of gender?”
One really common example is not wanting to be perceived as a man or a woman — but merely a person, either of inscrutable gender or genderless/sexless. My friend calls it “bilateral dysphoria” — feeling uncomfortable being read as female, but also being uncomfortable being read as male… I can’t control how other people view me, not really, but I can find a sweet spot that looks right and feels right to me. I can adjust my presentation to be less feminine, but if it becomes too masculine, I also feel not quite right.
“Is it just too exhausting to move through the world that sees and treats you as female when you aren’t? Is the socialization too hard to escape in your own sense of body being connected to identity?”
Too exhausting to what? To live with? It sucks a lot of the time, sure. But I do what I can to thrive.
“ Can you have breasts and periods as simply the reality of “you”, like hair color or weight, without being associated with femininity or femaleness?”
Sure, some nonbinary people can. I feel this way about periods. I have no problem with having them and do not see them as gendered. Breasts are more complicated.
“Is wearing a chest binder just another way to surrender to society’s demands for sexualized gender constructs, not unlike the corset?”
No. Nobody in society is pushing me to wear a binder, it’s completely different from when corsets were obligatory. It also has very little social impact. Nobody notices when I have a binder on or treats me any differently. I am not read as a different gender when I bind. I am not sexually harassed less when I bind. Literally no one cares or notices. It merely feels better for me, some of the time, but not always.
“If you don’t want to be sexualized female, you can’t show your breasts, and you have to constrict your body, your breathing, be uncomfortable in order to make sure you match the world’s expectations of a nonbinary person, just as corsets constricted women to exaggerated a sexualized presentation.”
No I don’t. I don’t have to do any of that. You’re assuming a hell of a lot about me and how I live. I wear binders like, two days per week at most. Many nonbinary afab people never wear them.