mrbol, are you sure you have Red Claw? I have some experience with these shrimp and it is hard for me to believe they are able to catch and kill a dwarf puffer. Maybe the puffer was dead before the shrimp ate it?
I agree - they can catch snails, my Red Claws managed to wipe the entire 40 gallon tank out of
Melanoides tuberculata. Thay are also able to catch small, rather slow fish. However, they are not able to hunt down a fish (even a sleeping one) that occupies the upper area of the tank. Red Claws are good climbers, but rather poor swimmers. Or maybe they just don't like to swim

Or maybe they rarely attack when properly fed.
The favorite food of my Red Claws is other shrimp. They show how fast they really are if they want to

Interesting observation - when given algae-eating shrimp to eat, they don't touch plants at all. We have a theory (don't know if true), that they will eat plants when they lack some elements in their diet.