Well. yeah, a man dressing in woman’s clothing (outside of someone like an actor who is doing it for pay) is a transvestite. “Feminine gestures” not required. Heck, he could be a lumberjack ('cause that’s OK) with a full beard, a burly man’s physique, army boots, and a voice as low as a tuba but if he wears a dress, carries a purse, and wears false eyelashes for kicks … that’s a transvestite.
If a man lived in a culture where “men’s attire” was dresses and “woman’s attire” was trousers then a tranvestite in that culture would be a man dressed in pants.
Back in my distant youth there was also the notion that cross-dressing was a sexual fetish. Don’t know if it’s still viewed that way or not. But a transvestite, no matter how feminine the attire, still considers himself a man (I’m presuming male for transvestite - presumably, you could have it the other way around but I’m not sure you’d notice given that it’s considered acceptable these days for women to wear some pretty masculine clothing either for work or by choice).
A trans woman, on the other hand, isn’t wearing woman’s attire for kicks or amusement or as a sometime thing. She might not be wearing particularly feminine clothing at all. But she wants to be a woman full time. As best my understanding is - I’m not trans myself so I may be wrong on some of this.
Technically, Page didn’t say he was a man, he said he was non-binary and preferred he/him/his/they/them/their. There may or may not be elaboration on this down the line.
So… Page is a “man” or “nonbinary” because he said so. “Non-binary” means, as I understand it, not “male” or “female” but “mix of traits”. So maybe that person prefers short hair and a tuxedo but still wears make-up. Or maybe prefers short hair and no make-up but wears dresses.
I think there are a bunch of assumptions that people make, and given that society views are changing and this is outside of the experience of most people that’s understandable. It’s why we’re seeing speculation about Page’s marriage and career. In reality, the marriage is between the two people involved and none of our business. Page’s career is up to Page - he might be perfectly happy to continue to play Vanya on Umbrella Academy as a female character. Or maybe not. Or maybe Page has a contractual obligation he’ll fulfill out of a sense of professionalism. That’s up to Page and the producers of that show.
I gave the example of Eddie Izzard who describes himself as “genderfluid” - for his stand-up routine he has long worn dresses, a feminine hairstyle, heels, nail polish, make-up, etc and even dresses that way on his own time. Yet he seems to have no problems playing male roles for money, and sometimes dresses in a masculine fashion on his own time. I’d say that is someone who has been “genderfluid” or “genderqueer” or “nonbinary” for decades, but that’s strictly my take. The ultimate authority on that would be Mr. Izzard.