I have a Valentini Pufferfish and can help you with any questions you might have. His name is Spud and is by far my favourite fish, and I can't imagine a reef without him in it. That said, even the small Valentini is far from reef safe, so you should expect to encounter some issues.
Each fish is different, but for me, Spud will mostly leave my inverts alone. He has never attempted to eat any of my hermit crabs and aside from an incident where he attempted to nip a snail when I dropped a bunch of new ones in, he doesn't bother them either.
Spud will eat certain corals though. Anacropora, Montipora Digi, or any other crunchy branching Monti will be viciously crunched on, although he seems to give up after a while. He will usually taste every new coral I put in the tank and has killed a Trachy and Acans don't survive in my tank anymore. He developed a taste for the Bali Green Slimer too, but they survived anyway.
So it's been a bit of a guessing game with corals, but nothing too serious. If you expect this and understand that he will kill the odd coral now and then, by all means, give the Valentini a go. It's like owning a dog in fish form. Tons of personality and not a threat to any fish.