One area of overlap not mentioned yet is KDeclarative::Plotter KDeclarative::Plotter is something we found we had to create in Plasma as the existing solutions didn't cover simple use cases or high refresh rate well at all.
This framework absolutely overlaps with that, which is a good thing as we want to split KDeclarative up and the current plotter implementation has been repeatedly problematic. I can say that this framework acts as a good replacement for those existing places as well as the other custom pie chart code in the system load viewer applets. David