Gender structure
The gender structure, like many other structures, functions across two axes: actual gender, usually determined by biological sex, and contractual gender, determined by contract. Not everyone has a contractual gender, and unless someone has a very well-known contract their contractual gender isn't usually assumed by others.
Actual gender
Actual gender affect pronouns and most fashion, along with many titles and gendered nouns. For those without a contractual gender it affects everything gender would be expected to affect.
There are very few cases of transgender individuals, and even less of those who are accepted.
Contractual gender
Contractual gender affects contractual titles and certain relationship titles (e.g. the Evil Queen will always be a Queen and Mother Bear will always be a mother.)
It cannot be changed, as it was fixed to the gender of the template for that contract.