A filter is probably a good idea to deal with their mess. An air-driven sponge filter may be better if you're thinking of breeding snails. Those are the kind people use in fry tanks because there's no suction to suck up babies. I think they work just by hooking up to an air pump, and it uses the aeration to rotate a sponge on which your bio filter lives.
Don't know for sure, tho, because I have never personally used those baby fish filters.
As for substrate, you can go bare. It would make it easier to clean up. Most snails don't really care if there's substrate or not, as long as there's room to lay their egg jellies. For that, plants will help because they provide more surface area and habitat complexity. I would think the purification benefits of live plants might make those desirable, too. For that, you may want gravel or some other substrate. Altho you could do java fern or something else that can grow bare.
MTS (and other trumpet snails, I think) tend to bury themselves in substrate, so those might prefer gravel for that reason. They might only do that to escape predators, though, as I've heard their behavior is different in the absence of fish (they're out all the time).
Gee, how did I become the snail guru? Where my other snail peeps at?
As for the snail ban, I heard of that over at dwarfpuffers.com. I will read up on it and get back to you! Of course anyone else is welcome to chime in, too

Anyone? I'm feeling drained...