Well, the idea is just like separating the tank into many rooms for each puffer to have the own room. So yes have something working as a border line is great.
The idea of a densely planted tank is mainly used to break up the sight between puffers so even when they're close to each other, they still don't see each other and they think that they're alone in their own space.
It looks much better for keeping multiple territorial fish now :D
Once you have the fish and you see them start to bully each other too much. Re-decorate the tank again.I re-decorate my tank everytime I do water change as puffer fish are too smart and interactive to leave them alone for too long :P