I have kept two other toby puffers, and they are all pretty much the same. While I have never caught one in the act, I have plenty of hermit shells with holes in them. I don't keep snails with them, but I would guess larger turbos would be safe due to thick shells. I do know that mine love stomellas, though. I also keep the guy I have now with 3 starfish and an urchin and he leaves them alone.
As for feeding, they will eat anything. Mine eats squid, silversides, scallops, shore shrimp, mysis, and rod's food.