Very late to the party, but that MA thesis on Jonathan and Mina's gender presentation that circulated on Tumblr some time ago (Jonathan, Mina, and the Holiest Love: Intimations of a virtuous queerness in Dracula (1897) by Viktor Karlsen Hessen) really is so, so good. From a deep dive into Jonathan as a Gothic heroine, complete with step-by-step comparisons with an actual Ann Radcliffe's heroine as well as the other female characters he's paralleled with in the text - Scheherazade and Lenore - to an exploration of how Mina's masculine traits are treated as positive throughout the novel and survive into the ending. Also, the author is very careful and rational when talking about Stoker's personal views and sexuality, neither jumping to conclusions based on a few facts nor disregarding those facts at all.
Also, there's a section comparing Mina to other female characters in Gothic literature who do not act in accordance with the Victorian gender norms but are punished for that - Helen Vaughan from The Great God Pan and Marjorie Lindon from The Beetle, and I personally am 1) always there for some The Great God Pan talk, 2) always there for dragging The Beetle.
