Is there a Matrix design document at a similar level of abstraction to [1,2,3]?

I want to use it, but the client (Riot? Element?) scares me with all its features, and I'm not sure I have a working mental model about what information is shared with whom and under what circumstances.

Is there a "blessed" client that doesn't run in the browser? Written in Python or Java?

[1] https://www.chromium.org/chromium-os/chromiumos-design-docs/... [2] https://www.chromium.org/chromium-os/chromiumos-design-docs/... [3] https://www.chromium.org/chromium-os/chromiumos-design-docs/...