Puffers get big, along with triggers. What kind of filtration do you have? Puffers are very messy fish. They grow very fast. Mine grew almost 4 inches in 4 months. Those sound like some big fish for a 75 gallon tank. Just a thought. i know a little about puffers, and not much about triggers. It sounds like perhaps these big fish will out grow your tank.
As for keeping puffers and triggers, you have to take caution. I BELIEVE (meaning not sure) that triggers can occationally pick on puffers.
By the way, how is your puffer doing?????