[Serious] What is “true” or “real” masculinity and/or femininity?

The serious answer is that there is no such thing, not objectively. Gender norms are social constructs. Societies can trend toward, and individuals can personally believe in, particular ideals for those constructs, but in the end they are arbitrary.

Another way of thinking about it is that “true” masculinity / femininity is whatever you want it to be, but only within the city limits of your mind.