I’m trying to understand the architecture, and wonder – as a user, do I have one source chain, or many, how are they organized? Does one of the pictured models represent what is actually occurring?
As far as I know, there’s one source chain per user per DNA.
There is a great Holochain in Action video on integrating the Playground visualizations into your happ: Integrating the Holochain Playground into your hApp - HiA 27 - YouTube
Screenshot attached, the source chain is on the left.