See, I'm less about top/bottom and more about dom/sub. I'm okay with any of them switching on positions, but I do have some preferences on dom/sub.
With my Buffy ships, Spike always subs, Angel aways doms, Buffy switches, Drusilla switches, Darla switches. Willow I actually think is more likely to sub and Tara do dom, but they can switch it up.
On Star Wars, Kylo/Ben is very, very sub. Rey and Hux are both doms, though very different types.
Most of my other ships I still actively read, I tend to think the characters switch it up at least some of the time, though maybe with preferences.
Re: Ships and switching
With my Buffy ships, Spike always subs, Angel aways doms, Buffy switches, Drusilla switches, Darla switches. Willow I actually think is more likely to sub and Tara do dom, but they can switch it up.
On Star Wars, Kylo/Ben is very, very sub. Rey and Hux are both doms, though very different types.
Most of my other ships I still actively read, I tend to think the characters switch it up at least some of the time, though maybe with preferences.