I like your point about day two. I find this true, even with in effect paid groups on a course that they feel the floor is too open or conversation moves too fast. Getting people to talk is so important to getting them to come back, and mostly because of a personal connection to that person. From my experience I like groups where a main channel for questions or chat is always active, so I know people are there, but the room I go to (often only notice one per “slack team”) ticks over at a pace you can keep up with only checking every day or two. It means you notice the other people and much more team dynamic.