Is a male-raised AFAB bad trans rep?

So I'm writing a fantasy novel. I have a character that is AFAB and brought up as a man as a pawn in a political scheme. Since women can't inherit in their world, they're disguised as a man because they're the only possible heir.

I was wondering if, with this context, it would be offensive or insulting if this character was transmasc. The general idea is that they feel very comfortable presenting as a man and feel more "right" as a man than they would as a woman. However, I don't want to perpetuate any negativity about trans people or write anything that could be used to hurt trans people.

I wanted the opinions of trans people (preferably transmascs/transmen due to the specific context of the question, but transfems I'd appreciate your input as well!) before I got too far into building this character.

If I were to have this character be transmasc, any advice on how to write this character's experience would be greatly appreciated! And if it would be problematic, I would love to hear any tips on how to avoid spreading misinformation/a bad image of trans people with the character being a cis woman.

(and just for a bit of personal background, I am nonbinary/genderfluid, but I would not call myself transmasc or claim to know the transmasc experience)