Ohohoho, an opportunity to talk about myself!
With trans characters, I think it's very important to figure out how much your character wants to transition and how far along they are in their desired transition. From my observations, it's generally easier for cis authors to write that are near or at the "end" of their transition. Throwing an extremely stereotypical depiction of gender dysphoria makes it very easy to see a cis author that hasn't done the research. The longer they've been transitioning and the more time since they've come out, the less their life will revolve around being trans.
As others have said, it's really important to make your character well-rounded and have traits OTHER than being trans. But there's also the issue of totally ignoring it, which also comes off as really unrealistic. You'll want to think about how transphobic your fictional universe is, and how much it fits with the tone of your story. If you're going for realism, make it like reality! But for light-hearted stories, there's nothing wrong with having some escapism from irl bigotry. I bring this up because in a more transphobic setting, a character coming out as trans to another will be a larger symbol of trust than in a world where it's more casual.
There's also mentions of childhood! I was in the girl scouts as a kid and have many tales, but I can't bring it up when relevant if I'm talking with people who don't know I'm trans. Depending on when your characters came out/realized they were trans and their parental environment, they may have had more "male" or "female" activities in their youth, since we gender kids pretty strictly (at least in western society). Again, think consistency in the world - if people are more accepting, it's more likely for them to have come out earlier and experienced a more "cis" childhood.
And one last small thing - if your going for realistic transition and hormone replacement therapy, Lavelie is going to be taking testosterone injections or gels for his whole life! I truly love the look on people's face when I explain that no, I'm only "done" with my weekly testosterone shots when I die. There seems to be a common misunderstanding that HRT "ends" at some point.