I have 2 dwarf puffers in a 8 gallon tank with 1 pygmy cory (he was a rescue) and a bunch of cherry shrimp. The puffers treat the cory cat like it's their child, and they ignore the shrimp.
Mine eat frozen blood worms, but I try to make sure that they get the smaller sized blood worms. The bigger normal sized ones are harder for them to eat.
My puffs were super skiddish at first, and it seems to really take quite a while for them to warm up to others. The male always hangs back and watches, vs. the female who is always up front to say hi. I have had them for about 6 months now and I love them!