I’ve had seramas, OEGBS, and sebrights. In my experience sebrights are a bit flightier and more easily frightened than my OEGBs were, but can be just as tame. Seramas are generally mellow with people and easy to handle. My sebrights and seramas both got along well with other bantams, I never kept them with large fowl. Sebrights and seramas aren’t really bred to be egg layers. I would say that sebrights are more like OEGBs in temperament, but seramas are a bit less skittish if you’re looking for that.
That has not been my experience. However, if the OP wants a larger serama, they can just get pet quality, which tend to be about the size of an OEGB.