Coincidentally, we just published an essay in Prism & Penn last week by Stephanie Moga called (and I might not be getting the title quite right) "Disappearing into Womanhood."
She writes that as a transgender woman her goal is to dress and present plainly, to disappear into the crowd so people don't notice her.
Many trans women cannot pass for cis, and worry about being clocked. Trans women I know tell me even if they can't pass, they can (do) work not to call attention to themselves. I'm sure that's not universal among trans women, but in my experience anyway, having known a lot of trans women over the decades, it's more ordinary than not. I've met lots of flamboyant drag queens, but I don't know that I've ever met a flamboyant transgender woman. (Not to say they don't exist.)
The author's goal to include LGBTQ people in their writing is admirable. We need representation in media and art and we can't achieve it just by producing our own media and art. But you bring up excellent points about doing the homework first.
Wanting to write about LGBTQ characters is an excellent first step. Spending time learning about the people you want to write about would be the necessary second step before the third step of actually doing the writing.