What are Type Group Bundles and Type Group Bundles list ?

It's all about bat entity sorting. Flexible. Can be changed as per your use case. It may be confusing indeed.
In https://www.drupal.org/project/bat/releases/8.x-10.x-dev → we have now a much cleaner menu. Easy to understand.

Please share your experience. How do you use BAT? Tell us about your use cases. How would you apply them to BAT?

Indeed, the concept of group bundles can be quite confusing. I have a use case where I need to rent a location either by individual rooms or by the entire venue. Can this be achieved using "Type Group Bundles"?

When renting the entire venue, all individual rooms should be available. Conversely, when the entire venue is booked, no individual room bookings should be allowed.

Use cases at #7 are not implemented into BAT module.