I would expect clients (App Views) to be able to use multiple relays in parallel if needed. That would be like having a local GitHub UI pulling data from several GitHub instances (“relays”) that may host different but potentially overlapping sets of repositories.
This would be like a Usenet client aggregating newsgroups from several NNTP servers.
Yes — the canonical source of truth for a user's data is their "data repository" which is analogous to a git repo. These can really be passed around any way you want. Our current relay architecture was designed to support large, real-time scale, but other configurations are possible as well, since all the pieces here are composable.
This would be like a Usenet client aggregating newsgroups from several NNTP servers.