A south american puffer should have 15gallons for the first fish and then 10gallons thereafter. This isn't due to aggression with these fish so much, but the amount of mess that they make.
I have my SAPs with otos and they actually shoal together sometimes which is great to watch.
I have also known people keep their SAPs with dwarfs and they are fine together, the only fights occured amongst the dwarfs. However with a 10 gallon, I would go with 2 dwarfs and about 3 otos, as dwarfs should have about 5gallons each.
Make sure that you get 2 females if that is possible (no wrinkles behind the eyes or brown stripe on their belly) and the fattest ones that you can find, to minimise the chance of them having internal parasites.