Murong Bo may have been babbling when he said it, but we sure heard it: "The Murong family has tons and tons of more martial arts on par with Canhe Finger," he proclaimed.
If this is really true, and there are > 5 other Murong arts that = Canhe Finger's power (which is a Great-level art), that would make Murong family one of the very, very best in its collection of arts. Not to mention, they had the arts of many other schools, although most were pretty conventional.
Which may mean that Murong Longcheng may have invented more arts than simply Shifting North Star.