I have been finger painting in SuperNotes for 30 minutes with various settings with both the build prop edit (150 to 300) and touchscreentune (Move hyst=0, movfilter=30) and I have to say, the difference is HUGE!
I went from not being able to read the scribbles to almost pen-and-paper quality. At this point the limiting factor is the fact that I didn't bring my stylus with me.
My current settings: per_sec = 300, touchscreentune move hyst=0 and movfilter=30.
Try these against yours and see how they compare. If yours are better, please post them!