pygmy cory cats will have a hard time disturbing plants.
Oto cats aren't really bottom feeders, but the are cool in groups.
Amano shrimp can't crawl out of a tank with no lid only, they need some sort of "ramp" to get out. HOB
filters and plants coming out of the water are good ways to allow them out, but it's easy to "escape proof" a tank.
Nerite snails, mystery snails and rabbit snails etc. etc.