I keep the following tanks
T. cochinchinensis - No tankmates, whatsoever, at all.
C. salivator and C.irrubesco - Hatchetfish, bristlenose plecs. Also had success with halfbeaks
T. lineatus - Panda garra
C. borneensis male - Siamese flying fox, harlequin rasboras
C. borneensis female - male and female pair of pelvicachromis signatus
T.biocellatus - Green chromide, Archerfish, 2 gobies, 4 mudskippers
I have also kept
Dwarf puffers with BBG's, bristlenose plecs
South american puffers with C.irrubesco
C. irrubesco with Dwarf puffers
So it's not impossible, but you have to choose tankmates carefully. For instance, a betta would not work, nor do i think congo tetras would work. Long finned species with any puffer I think would be asking for trouble, and I've lost a few fish because my puffers have not tolerated them (they do at first, then usually change over time).
But on the whole, no they are not a fish you could merely add to a community, some care does have to be taken over tankmates.
As for where to get snails, find a friend with a garden pond.