I have seramas, silkies, polish, german spitzhauben (sp?), campines and standards all together (VERY large indoor coop-about 1120 square feet, then in the spring I open them up to range in a 3300 square foot run)...no problems except for 1 feisty serama roo, he sends everyone to running!! I think it depends on how much space you have for them.
I let my OEGBs free range with LF, and they are as small as sebrights. No problems at all with the large hens. My worry is that they are an easy snatch for the hawks or cats, but they love free ranging. I don't free range the seramas because I don't want them breeding with the OEGBs.
They are not very big, and can FLY really well. Mine don't free range unless I am out there with them because we have hawks in the area and they wouldn't fly away because they love the mealworms I have with me way too much. But they can fly up into a tree, across the yard, pretty much wherever they want. I don't have any large fowl, but do have them in a smaller flock situation with easy-going birds that they get along with well.