Hello corylover! I keep a pair of dwarf puffers so I will try to answer your questions based on the experience I have. Firstly, what kind of lighting does your 5g tank have?
I would suggest a lot of low-tech plants as I imagine you probably only have a lowly lit 5g setup. These plants include Hygrophilia (water sprite, water wisteria), Crypts, Java Ferns, Anubias, Staurogynes. There are many others but these types I have had great luck with.
Bog wood is a big plus, these guys are very used to having wood in their environments, and although yours is probably tank bred, I am a firm believer that the conditions created by having wood in the tank go way further than just making the fish comfortable. These guys respond very well to light tannins released by wood, it seems to keep mine very healthy. With the java ferns and anubias, you can attach them to the wood and create a leafy piece of wood that looks WONDERFUL!
I have been unsuccessful at keeping a snail population breeding with my puffers. I put a bunch in hoping they would populate and I just ended up with piles of rotting snail shells on the substrate and no babies. I did find that at my local pet store they are always trying to get rid of pest snails and will bag me up a bunch of them for free, so i just feed them a few here and there, they get switched off from those, frozen bloodworms, and live brine shrimp(their absolute favorite).
Hope I could help a bit!