Phew! It is all chromosone dictated. You are either a man or a woman; male or female.
If you decide to take hormones of the opposite sex or have surgery, your body will change, but your chromosones will not.
I have a friend who changed male to female - I still like her (as I must now say), but also this poor person looks like a pantomime dame with male facial features (including a big hooked nose), huge feet and 6ft 6 tall. No way could she be thought to be a woman.
I think it is very sad that he was so unhappy in the body given that he went through all this surgery (with many dangerous complications) and other life-changing interventions.
I think that it is fine to make the choice to do this, but that intact males can call themselves female if that is what they wish, but not fine to enter exclusively female spaces.
I also think that people should not be frowned upon if they fail to spot which gender someone is saying they are.
There was an interesting thread on Mumsnet where a school teacher announced to her Yr 7 class that she was gender fluid and they could call her Miss X, Mr X or Dr X as they so choose. How very self-indulgent to put these adolescent pupils in that uncomfortable situation, giving no thought to them but just to oneself. Silly woman/mad/neuter!