Puffers like established tanks, plan to have a wait period from the time you start to allow the tank to cycle completely. IME that white fungus happens about a week after you add the driftwood. The best way I found to fight this was with Siamese algae eaters, they love that white algae. Spot treatment with excel would probably work but I haven't tried it with white fungus/algae. As far as aggression goes, since it seems like you're not looking for tall plants, go with tall hardscapes. You want to reduce the line of sight as much as possible.