In my experience, all puffers, including pea puffers are highly intelligent and enjoy the thrill and puzzle of the hunt as much if not more than the food itself. So even if a pea puffer is stuffed full, it'll still have fun murdering every snail it can find with its clever eyeballs.
I stocked my pea puffer tank with trumpet snails (highly recommended, because they're a little less palatable than other kinds, can reproduce asexually, and they burrow in the substrate, which gives them a fighting chance), ramshorns, bladder snails for a few weeks before getting my puffer to help get their numbers established. But the puffer still eliminated them all within a couple weeks.
So now I harvest 8-10 small snails from all my other tanks to feed the puffer every couple days. I don't bother crushing them because I feel guilty enough sending these pretty ramshorns to their death, and because I always pray a couple will survive for at least a day or two to help eat up some of the puffer's leftovers and some of the algae on the walls. It's definitely the only tank in the house with enough algae to eat!