Gender isn't real.
Sex is. Humans cannot change sex.
Gender is a mish- mash of stereotypes that change depending on time frame and location. What's masculine in one country is viewed as feminine elsewhere. These stereotypes influence everything, clothes, language, body language, emotions.
I am critical of stereotypes associated with gender. There is no one way to be male and no one way to be female.
Clothes have no gender. Some clothes are based on sex (ie bras) but if a man has moobs and finds support in a bra so what? Him wearing a bra does not mean he's a woman. Just like me wearing boxers or trousers mean I'm a man.
Men can be nurturing (emotion normally associated with women). Women can be aggressive (vice versa). BUT these are stereotypes!!!
Right wing or conservatives also believe that sex is real and that humans cannot change sex BUT they like gender stereotypes. Women must be feminine, caring etc. They aren't gender critical as I understand it.
As for numbers of trans people - well one trans person surmised that there are as genders are there are people on the world (I truly think they are mixing up personality and gender!)
Honestly I do believe there are some people who experience dysphoria but those numbers are not as high as we might think.
Maybe 1 or 2 people in a million really, truly wants to alter everything about their body and even then they should start with therapy to work out if the changes they want to make are right for them.