Food, selfies, and toy posts tend to average about the same per post on Pixelfed. 8-10 likes on average.
On Insta, selfies, manga, and cats do best. On Pixelfed, cats, flowers, and selfies do best.
Basically, on either platform - you can't go wrong with cat pics or selfies.
Now, on Insta, part of the manga boost is that I've been kind of into Mangagram - sharing posts, interacting with posts, etc on manga. Then again, I don't see a lot of manga in general on Pixelfed. Maybe it's me!