Depends on the puffer. I got a dog face puffer years ago in a tank break down along with a queen angel they came from the same tank and were together for a couple years is what I was told. About 2 weeks of them in my system and the puffer killed the angel. Most of the time the porcupines are a little less fish aggressive had one in the past also seemed to get along with the other fish he was with.
I’d say it depends on the individual personality of the fish while puffers don’t generally eat fish I’d avoid smaller fish and ones that can fit in their mouth especially if it’s a lot bigger than the porcupine and as it gets bigger. Mine leaves all the fish alone but every puffer is different.