I think it’s difficult to predict what the audience at any given site will devour and what they will ignore. Trends do tend to come and go. Last time I checked, werewolf and kidnapping stories were the most popular in the M/M original areas. I don’t know if that has shifted yet or not. The appeal of high school drama erotica seems to be an ongoing thing in general, but I have no idea if that is applicable here on AFF.
If your priority is to focus on the trends, I’d suggest going through your chosen category (or similar categories if yours doesn’t have a lot of traffic in general) and look for patterns in dragon prints and review counts. I’d like to tell you which of my stories get the most attention, but I don’t actually post most of what I write, lol. I wish you luck!