Most settings applications (GNOME Settings, KDE Control Center) give very limited access to managing lower level components in the system. For example, kernel management, managing groups, etc.
If they did though, in your opinion, what would be the most effective way to offer a simple experience for some users, and more control for those who need it? How would most desktops implement this “hybrid” approach?
Or should users not be able to control those things graphically at all?
For power users yes, not for beginners. There is already a set of graphical tool which can control various lower level stuff for power users. The wonderful YAST (OpenSuSe), webmin and the acockpit project jumps into mind. I could see it both ways, but if it would be integrated into the desktop environment settings application then I would lock it down behind some “Up, Up, Down, Down, Left, Right, Left, Right, B, A.” to make sure that it isn’t the first experience for new users that they bricked the system. BTW it is a separate app(s) on windows as well, on MacOS you get some of it in the system settings.