I hatch out all kinds of breeds together-havent had a problem except with the turkey tom! I wouldnt pen them seperately unless you want purity in your flocks for hatching If they get along ...Great!
I just put my silkies (8 weeks old) in with standard chicks (4 weeks old) and have had no problems yet, since they are all roughly the same size. Just make sure they are the same size and keep a close eye on em! I housed mine in cages next to each other for a few weeks before putting them together just by chance so that may have helped. I have room to separate them should the silkies start getting picked on, but they are slightly bigger than the standards so I hope that helped.
My standard chicks live happily with my two silkies AND the cornish Xs. Ellie Mae, my red silkie, bosses the CXs around, it's a riot. I worry non-stop about the silkies being hurt by the big birds, but everyone is thriving.