@HeidiOberrieder My thought is that this set-up is just far too complicated to pull off on Canvas. You have apples and oranges in terms of group work vs. individual work, and then in terms of the number and types of assignments.
First, If you would like your students to work in groups, have everyone work in a group. Is there any reason why some of your students can't work in a group? You can make a group project, but still grade students individually based on their participation.
Second, I would strongly encourage you to create the groups and place the students in the groups yourself. You can randomly allocate students to groups, or you can create groups based on your knowledge of the students. The idea of having the students self-select groups is just going to create problems. Either cliques will form, or some of your students won't figure out how to join a group.
Lastly, this complicated scheme is going to be a real pain when it comes to your Gradebook.
Make this assignment simpler for yourself and your students. I don't think the time and effort you're going to spend trying up different configurations in Canvas will be worth it in the end.