I have a few mixed breeds roaming around in the paddock together including polands, warrens, pekins and silkie crosses, they all seem to go around in their own groups and then at night time waddle back to their own hen houses for bed!
I find when introducing new hens, keeping them seperate in a secure run for the first few days is always best, the older hens can get used to them and when then let out to intrigate there is no bullying.