tersely, i think that sexual orientation is neither fixed nor inborn, and i insist that this is actually the scientific consensus. the calvinist gloss is political and to an extent legal (you can't execute somebody for sodomy if you can't demonstrate mens rea, so the delusional claim that the gay man had no choice actually saved lives, and this is a historical and factual truth, it has, and it may continue to, but it's just not true). they have spent half a century scouring the genome for a gay gene at this point and it's not there. i think with orientation that there are conscious and unconscious factors; in the end, there's a choice made or not (and in liberal democracies we respect individual choices that don't create harms, we don't criminalize harmless behaviour, or legislate our normative morality), but the pavlovian conditioning leading to arousal in one situation or another is largely the result of circumstance, coming out of a sexual orientation tabula rasa that we are born with. it's only the case that most of us are straight because it's what we teach our kids, and that is a general truth in all mammals. mammals are not born with instinct; mammals need to teach their children everything, from how to eat to who to fuck. it is entirely plausible that we could teach ourselves to be majority gay, if we wanted to reduce the population. there is no biological reason that couldn't happen.
gender identity is a reflection of personality aligned to gender norms, which are a social construction, so it's an entirely arbitrary decision and it's ultimately up to the individual to choose if they want to transition or not. i know extremely effeminate straight men. this is totally random and absolutely arbitrary, and also subject to change, although we tend to be kind of stubborn. the idea that there's a gene for pink lipstick is pretty stupid and fundamentally misunderstands what a gene is.
that doesn't mean it isn't obvious. from about the age of 16 to about the age of 25, when i started getting more serious about transition, almost everybody that i met figured it out.
when i told my sister around the age of 20, her response was "obviously. why did you wait so long?". this is particularly noteworthy given that she grew into an anti-trans hard-right bigot.
and i was just remembering the day when i was working the cash at an a&w and the somali girl i was working with, along with my female manager, unilaterally decided, without asking me, that i had "girl power", too, which was a spice girls thing. these girls had no way to know anything, other than to guess based on very rudimentary interactions with me and while it was certainly intended to be inclusive, they might have made the opposite choice; they also very clearly stated that the guy in the back flipping burgers did not have girl power, to which he responded with an annoyed 'cmon! that's not fair!".
but, i was working the cash in the first place because somebody in management decided i was female for me. in fact, they told me point blank they wanted me on the cash because i had a pretty face. this was pre-hormones, and before i even came out as trans. i was initially hired to work the fries stand, but that lasted all of a half of a shift before they moved me to the cash register, and i worked that job for something like two years. they moved me around all over the city, even. i was their prized pretty faced cashier. generally speaking, fast food is a pretty gendered work force, but this particular manager had a strict gender segregation policy in place, as well; when i met employees in new restaurants, they would consistently express surprise that i was on the cash, for about an hour, until they got how obvious it was.
when i was in grade school, several of the little girls tried to force me to use the women's washroom and a teacher had to intervene and discipline them for it. i want to be clear about this: i wasn't trying to enter the female facilities. they wanted me to use the female facilities. like, they wanted me to go in there and gossip and play with my hair. they thought that there was something incorrect about me using the boys room and tried to take matters into their own hands to fix it. this one little girl had me totally figured out in the fourth grade, before i had the slightest clue, for myself. i described myself as like a girl not as a girl. it took me quite a while to come around to make that choice that this kid had figured out for me when she was 10.
i even got hired to work at a makeup store called the body shop at one point, as an entirely pre-hormone cismale.
so, i mean, it's a choice, but it's one that is framed in reality, as well. it was christopher hitchens that put it succinctly when he said that you shouldn't have to insist that you're a lady; if you're actually trans, the people around you will realize it, and they will either accept you or denigrate you for it. it's not something you're required to act on, but it's not really something you can hide, either.