It would be nice to have all 3 group/community levels
-- subject matter community (open to new members)
-- friend group (only invited members, but not necessarily needing encryption)
-- secure group (private and encrypted)
The secure group probably would require a private relay. The others could be public.
Yes!! You could even make some parts private (chat) and others open (library and articles). That would help you find new members.
You could even have multliple chat channels with different privacy levels. Like on Slack.