I've got a candy cane pistol shrimp allegedly someplace in my tank. I hear clicking every so often, which I assume is the shrimp. Haven't seen it since I added it. lol good luck!
I have a Valentini puffer and a pistol shrimp in a 65g. No issues what so ever.
My Goby protects their house so no fish ever comes close.
Once you put the shrimp in he will most likely hide immediately. I would recommend maybe introducing him when the lights are out to make sure the puffer doesn't go right after it.
I also have a Coral Banded Shrimp in there but the puffer doesn't seem to care. Nassarius snails however won't last very long lol.