I personally don't respect people's wishes to be called "they" with no alternate pronouns. I don't allow them to dictate changing the way I use language, and I don't really buy into the whole "non-binary" thing. IMO it always comes from a place of promoting societally ingrained gender roles, and I don't agree with that. Like "I don't want to be called 'she/her' because all women like pink and wearing dresses and that doesn't apply to me".

I will call people whichever of he/she they prefer. If someone is presenting as male I will call them he/him, and if they are presenting as female I will call them she/her. If they are presenting but not really passing I'll still respect that they're making an effort and call them whichever they are trying to present. Eg. There was a trans girl in my MTG club in uni. She did not pass at all but I'd still use female pronouns since she kept referring to herself as a girl and I'm not trying to make someone feel bad just because they were born with the wrong hormones.