Copies and convergence
Every member is designed to keep the complete encrypted log of each space it belongs to and to fold it, that is, apply each change in turn, into a local SQLite view. Reads are local; they never wait for the network.
Writes converge: the same set of changes yields the same state on every member, in any order of arrival. Each field type says how concurrent edits merge. A change that loses to one its author had not seen stays identifiable as such, the same way on every member.
In island mode, with no relay at all, members keep working. Network gone? Your writes are stored locally and sync when the relay is back.