I think the way your tank is laid out with 2 sides it will help with aggression. It's better when everyone isn't always looking at everyone. I'd do what Hobbzz said and get one of each genus.
If you get a powder i'd 100% QT and treat them like they have ich because they probably do even if you can't see it.
If you get a powder i'd 100% QT and treat them like they have ich because they probably do even if you can't see it.