Given the choices of BR or BO I would go with a BO any day. Mine are mellow and sweet. Not an aggressive one in the lot. Giant cardboard boxes work well as brooders too. For friendly I think my Delaware is by far the friendliest followed by the Speckled Sussex.
Might get both if they have them available mon. One of each plus an EE would be great. A cardboard box isn't cat proof unless it's in the dog crate.