I don't think so. I've never heard of 'Margary American Horror Story' in relation to the official American Horror Story series. It might be a made - up or misnamed thing.
I'm not sure what 'ost American horror story' is supposed to be. If we assume it's related to American Horror Story, that show has been evolving and presenting different horror ideas over time, but it's not something brand new in the grand scheme of horror as a whole. There are always new shows and movies trying to bring fresh takes on horror, but American Horror Story has been part of the established horror television landscape for some time.
Well, the cast of the new 'American Horror Story' usually features a mix of both veteran actors from previous seasons and some new faces. Some of the well - known actors might return, like Sarah Paulson or Evan Peters, but they also introduce new talent to keep the story fresh.