But when naked, with no adornments, how can you even tell that this is a trans woman, and not simply... a non-trans man? Are we talking someone who's had "feminizing" medical procedures here? If so, which ones?

This isn't without risk, but if you want to get a good handle on it, I suggest viewing the pornographic material. There's ample data available on Reddit to get a general understanding.

but what about high-heeled shoes?

You made my point. It's high-heeled shoes, yes. They change gait. Flats are not fetishized AFAIK.

Sure, except... why only for women? Aren't health, being blemish-free, and gait important in MEN, too?

Men are more concerned about looks in women, because of basic reproductive fitness. Women are more concerned about social status and wealth in men on the basis of long-term support of the offspring. It does not mean that women flat-out don't care about looks in men. Reproductive burden is very high in women.

And yet, the most desirable female "type" is often THIN. How do you explain that?

Simple, they're still ovulating, despite being thin.

So I think that the basis for these accoutrements is what the female gender-role boils down to: "inferior". Specifically, to males. Thus, whatever a culture associates with lesser/subordinate status (especially if it caters to male preferences) tends to be automatically coded "female". Such as being decorative, a sex object... trivial.

Class power hierarchies, or interpersonal power. Well, certainly there are sadomasochists out there that eroticize these concepts, but I wouldn't quite go so far to say that heterosexual men are inherently sadistic, in the paraphilic sense of the word--pain, power, humiliation. There's a pretty large gap between the paraphilic and the euphilic, I'd say it's qualitative, not quantitative, but I could be wrong.

In the case of Chu, "The truth is I have never been able to differentiate liking women from wanting to be like them," that's classic AGP. Some researchers have suggested that people with one paraphilia often have another, so you could very well find masochism in Chu.

AGP latches onto stereotypes. AGP does not enculture itself with feminisms before deciding what ought to be erotic, and it starts at an early age, long before a person has the life experience or faculty to have a nuanced view of men and women.

I think we're on the same page insofar as we can look at atypical sexuality as a useful tool to inform our understanding of the majority phenomena, but we do have to be careful to prove out the hypotheses.

Hence their sexual response to "weaker" men in prison

Which does not surprise me, but it's a constrained situation, because there are no women available. I'm assuming that they are employing fantasy to obtain arousal and gratification, and the closer a flesh and blood person is to the heterosexual ideal (in this case, a woman) then the easier it is. There's also the issue of sexual economics and coercive behavior.