My coop is 9x12 and run is 14x16. I had the little ones in one of those cheap Rual King coops inside the run for about a month for a no touch see em approach before I let them together.
They free range together... I say together but rather two separate groups and the big ones don't bother the little ones. In the coop it's a different story. It's like the newbies are pretty much scared to go out into the run and stay in the coop on the roost or poop board unless the big ones are out in the run.