Be sure that you put them where they can see each other but have no contact for a week or so before you integrate fully. They make get picked on quite a bit if you don't. They will still get the occasional peck but this is normal and nothing to worry about.
Right. And when you do mix them. either hand place them on the roost at night, or provice a lot of distraction so they have something besides new birds to think about -- a bymch of hay or straw spread around, plus a bunch of greens or similar busy-making treats.