I also uninstalled Unreal Engine from the machine to free up space. That could be related to it as well as I have/had the Unreal Live Link Plugins installed
Ah... I also uninstalled Unreal Engine to free up space and because it wasn't very usable on the machine anyway together with iClone. It might be related to that.
The problem has disappeared. It seems to be fixed with the latest versions, but only after reinstallation. I had updated right after the update came in (I think yesterday?) and checked again then - but the problem was still there. I reinstalled CC, iClone and Cartoon Animator today because I had to move the content to an external disk and only during install you can change the template library paths. Now they are behaving just fine. 0% GPU and very low CPU. I will do the same on the other machine to see if it helps there, too.