I usually write Crona as female because Crona is feminine in my opinion, and I relate more to this. I have written Crona as male before and am not afraid to do so, but unless prompted to do it, I usually choose female. When talking about Crona, I tend to use gender neutral pronouns. When speaking to a friend who is using he/she/ze, I will likely use whatever that friend is using for the duration of our conversation.
Though I prefer female for Crona, it doesn’t matter to me what sex Crona is. Either way Crona is still Crona, regardless of society’s binary boxes. There is no official sex/gender for this character, so it's not worth arguing over.