It sounds like you want a group set up in your courses called blended learning and a group called distance learning. Then if all activities are classified as Separate Groups the posts by the Blended learning students in the same forum will be separate from the posts of the distance learning students. All students will see the exact same forums, assignments, and resources. So when a student initially enrolls in the course they are putin the Distance Learning group. Then if they upgrade, they are moved to the blended learning group.
Groups is most often used for different sections or periods of the same class. It helps instructors use the same course, but keep the groups of students separate for easier grading. S