So far mine hasn't harmed anything in my tank. A couple days ago it and the goby moved right under my CBS and they about had a fight over a pellet. It's fun watching it push sand around though. Sorry but no clue about the puffer.
On a side note, if you do decide to get a pistol shrimp get a shrimp goby for it to pair up with or you might not see it much. Or at least I think thats what tends to happen