Hello @Brandon !

1. Yes, Spaces have the option for the paid join.
2. Commonly - Spaces may have parent / child paces, but it's better the idea from the @Andrey B post here https://unacms.com/p/una-9-rc8-released-with-post-to-context
3. Yes, you need to have the installed Notifications app.
4. Right.
5. Certainly - see the point 3 above.