Your point about not matching the length has me thinking about "Mr Rowl", which I've just finished a re-read of. There the smarm-y m/m relationship isn't even introduced until halfway through the book, but when it is there's an awesome conflict of duty and loyalties over it. Meanwhile the romance has some conflict caused by things always going wrong with Juliana's attempts to save Raoul, which continues all the way through the book, though it isn't always the focus.

Yeah, I don't think there are any general points here! Other than that I think Broster likes Honour and Loyalty etc. more than any particular types of conflict or anything else. :D