As someone learning Wordpress for the purpose of customizing a Buddypress installation, I'm looking for a graphic representation of how Buddypress works and augments a standard Wordpress Multi-User installation. There are a number of examples of Wordpress diagrams including this one by Yoast.
I don't think there is one.
The only difference with BuddyPress on multsite verses single is.. .the users get blogs.
As for the buddypress theme itself. The bp template pack shows exactly what template files are used as extra. They are all labeled according to their use.