As many other people have said before me, I think people are allowed to understand their identity and express masculinity/feminity however they wish (unfortunately I feel it's necessary to say that fetish wear should be reserved for consenting adult situations and not worn to the office/classroom). I don't think they should be harassed or discriminated against. But they also have a sex, however the wish it were the other and I don't think it does them or anyone else any good to pretend they don't or that it never matters.
But they don't get to demand everyone believe the same thing about gender identity or pretend that all the single sex services and groups set up over decades are really about gender identity not sex.
They don't get to redefine the meanings of all words from woman, lesbian, homosexual etc. and demand everyone obey their new definitions. Or compel pronouns. If you commit a sexual or violent crime reporting and court proceedings should correctly identify sex even if also stating a gender identity. Victims should not be forced to lie about their attackers sex.
Where sex matters - esp. hospitals, care settings, residential trips, toilets, changing rooms, refuges, rape services, sports, awards/inclusion measures for women, prisons etc. They ought to use the facilities for their sex.
Where sex doesn't matter e.g. all mixed sex settings, they are already accommodated whatever their beliefs. Add in a whole bucket load of extra acceptance for people who are gay, gender non conforming, disabled etc since this is my party.
I think people should be able to have same sex social groups and meetings or same gender identity groups and meetings. Because people should have freedom of association.
However in my fantasy future I'd like them to be upfront about which thing this is rather than pretending to be single sex and actually being mixed. So people can make an informed decision and so mixed sex organisations do not get funding specifically intended to help the inclusion of female people.
So if adopting mixed sex inclusion policies the Girl Guides were called the Child Guides, and the Women's Institute were the Feminine Feelings Institute that would make things much clearer.