Ultimately, sex is defined biologically by gametes. You produce large gametes (ova), bear the young and lactate or potentially can do so you are female. If you produce small gametes (sperm) which fertilise the ova you are male. The other characteristics like chromosomes and hormones go with that. It actually is that simple, and rarely goes wrong. Even those born with endocrine or chromosomal problems can have their sex defined using that definition and we can work out whether they are a sperm producer or an ova producer.
I don’t feel threatened by transwomen, but let us face facts. They are male and your sex is neutral as a any other fact about a person. The whole purpose of this definitional and semantic debate is to shoe horn males into female and woman somehow and stop anyone discussing the facts to this end. It’s about who dominates and where, and women are not allowed to dominate even in their own spaces. That’s why there is frenzy every time someone speaks about female only functions and roles. As someone said recently transwomen are transwomen and I will add it is worthless trying to change the whole world to make it so they are women (and even then they don’t seem to be at all keen on being treated like women and being subject to male violence even though the pretence is they suffer more somehow). It’s simple. You have to be female to be a woman.
How about just be yourself, it’s OK to show your personality even if you differ from the stereotype for your sex. You should not have to change your body to comply with those stereotypes. If you differ from the norm, well, you are the same as everyone else who isn’t a stereotype of the supposed norm.