I've seen arguments for both? But I see "topping" as more of a kink, and like the idea of them as switch-hitters. They take turns given on who needs it at the time. Though Hux topping from the bottom is a particular kink of mine, I'll admit. I do like the idea of Hux domming Kylo and making a mess of him, as well.

Basically I'm pretty open to either.