Bottom line is we have no way of knowing or understanding how anyone else feels inside their self. Sometimes we can get close or recognise things if we work hard a thing listening to other people, or if we've walked in similar footsteps. But even that's tricky.
Empathy is a challenge for a lot of people.
On the whole, I don't believe it's necessary to understand someone else's lived experience in order to accept it as real and endeavour to be inclusive of them.
Lots of things we humans think and feel go way beyond what our language words can manage to describe anyway.
And trans stuff is particularly limited by language because the language, in English at least, struggles to use neutral gender when it comes to people, or to differentiate between sex and gender in a way that gives common understanding.
So I have no idea what it feels like to be a trans man like my friend, and he has no idea what if feels to be me. We both listen to one another, and try to empathise, and learn from one another what the things are that wound so that we can avoid saying them or doing them.
And we each help other people learn those things too so that they in turn will be less likely to be inadvertently hurtful to someone else who they encounter someone who is trans, or has experienced the non routine shit that's been in my life.
Meanwhile, lots of people all over the fecking place like to write about what they think it would or should feel like, or say they get it, or we're doing it all wrong, or they wouldn't do it like that, or they'd just kill themselves if it happened to them etc.
Anyway, waffle whiffle.
Point being, we don't need to understand or be able to articulate stuff exactly to our own satisfaction in order to not be arseholes about it.