Hello Jonathan. Please check the following:
- Groups which are classes of learners in courses and Cohorts which are classes of learners throughout the site. (I think in the questions you are referring to, the key points are "site" and "course".
- Restricting access to courses - I am not sure which question this relates to?
- Sign up issues - I think you are referring to a question about users not receiving an email? This is covered in the page Enable sign up.
- OAuth2 - I agree this is not dealt with in depth; just shown in the video on the page Explore user management. I've made a note to improve this; thankyou.
- Cohort sync is dealt with in the video on the page Cohorts as in my first bullet point.