Questions with no good answers. I believe a space is not truly open unless all are welcome. To me, Pride is a celebration of all things queer, and anyone who agrees with that is a good addition to that space. It's controversial, especially regarding Pride's roots in advocacy, current commercialism, and shaky stance with many people of color.
The two-sentence explanation of the terms non-binary and genderqueer was all I could fit in this comic, but it's worth looking up to learn about the history of these identities. Could be a book.
For every identity, the potential for a flag. Wave it or not, but be proud of who you are.