The set bonus is on the armoring on War Hero level gear and higher, so moving the mods will keep the set bonus. Anything below that (Battlemaster basically) is on the actual shell and cannot be transferred. So you'll have to wait until you have WH to make the move to different armor.
As to the second question, yes, you can use any orange gear and it will scale. If you check out any orange piece without anything in it, it has the same stats assuming it is the same type (light, medium, or heavy). As long as you are using the correct armor type for your class, you can use anything you'd like or take advantage of the adaptable social gear for any class.
Thanks for the reply! Also what if I have already put mods into the orange and want to swap them out for better mods will it scale again? Does it have to be adaptable?