You may well want to test this before you actually do it. I have a colleague in another university working on 2.2.4 (?) who tried it. Somehow, he attempted to use groups and groupings it ended up not showing grades to the students for those two assignments. The grades were there for his grade book and calculated in the total but not shown to the students. No matter what he did, it never worked properly and for a few students he could never convince them.
Students that that were not getting the grades they wanted took it to task. They squawked over and over again and accused Moodle to being totally faulty and unreliable. He was ready for parents to start calling him.
To this day, he never figured out what happened. He doesn't know if it was a bug or something he did wrong. The term is over and hopefully the rumors will go away.
All I can say is talk about it and test it. maybe someone here can explain what happened or might be able to help you avoid the problem. Maybe it will never happen again.
Personally, although I am working on a different version, I am not going to touch groups and groupings until I see it working correctly on some other system first.
Stung once, Forever cautious.