I don’t know if I’m the best person to answer the question about kind:1 notes.

The couple groups I’m thinking of are private. Although I’m sure there would be a demand for public groups as well.

The functionality that we use is almost like a closed version of Facebook - posts to the whole group and then conversations on the post. (I prefer chat-based groups, but people are comfortable with the post/comment structure.)

Many of the Twitter-like clients could have this feel, if instead of signing up, then joining a bunch of relays, and then following people, you just signed up and joined a group. Maybe the group has an npub (or similar type of public key) and when you sign up it just asks you for the groups key.

Honestly, if I understand relays correctly, this could be done with any client and a dedicated relay. For example, I’m in a “educators for heterodoxy” fb group. I could just set up an “educators for Heterodoxy” relay, direct group members to a client, and have them only subscribe to that particular relay. Then our feeds would just be from each other.

Maybe I’m off on that - just thinking out loud. (And I don’t have the time or expertise to actually run a relay, I’m just thinking hypothetically.)