If you are going to have a niger, the other trigger I would suggest in a 10 gallon tank would be a assassi, humahuma, bluejaw, sargassum trigger. If you had a bigger tank I would suggest a blueline.
Puffers- try porcupine puffer, or sharpnose puffers (canthigaster sp.) They are a smaller puffer at 5 inches MAX, but don't worry the triggers won't bother them.