And have you interacted with any of these people on a regular basis? Do you use their preferred pronouns or do you use your preferred pronouns for them?
When you think of them, do you think of them as their preferred gender or the gender you prefer for them?
Those are good questions. When it came to my son's friend, when I knew her and was interacting with her on a regular basis, she was a her. By the time she came out as a he, they were in mostly in different schools, and I never saw her in person again. She showed up to eighth grade graduation in the boy uniform, which was the only time I ever saw her in person as a boy.
As you can see, I'm using "her", because that's how I knew her, but I'm pretty sure I would say "him" now. I say that she went to school with my son, but I say that he is currently attending Michigan State. I don't really think of him as either, if the truth be told. I think of him as trans. I know a little bit about where he is and what he is doing because I sometimes read his parents' blog. My son and he drifted apart, as happens when schools change.
Just to add one thing. He is definitely one where the trans-ness appeared very early. I remember driving a group of 10 year olds to a birthday party where they were discussing whether she was "really" a girl. None of those kids knew what transgender meant, and I didn't bring it up. When my son was 13 and wondered aloud if she might be gay, I said I doubted it, and then described to him what transgender meant.
In high school, he used separate facilities, which seems very wise to me. He may think about himself as a boy, but he was very much aware that getting naked around a bunch of teenage boys just wasn't a good idea.
As for my recent friend, I think of her as a woman. Maybe that will change in post-pandemic times when we are once again interacting personally. I'm not sure if she thinks of herself as a man, or as gender-neutral. She wants "they". We do martial arts events and get very sweaty sometimes, and at some events, showers are provided. From what I know of her, I don't think she'll join us in the men's showers.
There are a couple of passing acquaintances of mine that are MtoF trans, but no actual friends, so I don't have personal experience with them.