The idea is actually not to have inbox and outbox sections at all, but a "personal relays" section that smartly manages read/write flags behind the scenes. If a relay requires auth to write, the client should (could) disable the read (inbox) flag.

The average person should just add a couple of big free relays and maybe a couple of paid relays. No need to explain much to new users; as soon thwy will understand more about Nostr, they will be free to tweak the details.