Ambush scarab of cointainment, rogue exile/number of monsters

I wanted to optimise my tree a bit more and wanted to know if strongboxes capture rogue exiles, so if you have 20 additional rogue exiles, would that end up being 20 additional strongboxes?
Also when you have the nodes that have increase number of magic/rare monsters, is that seperate from "pack size" which would also end up being additional monsters?