After a few more experiments, I think that the problem lies more with the complexity of a brush tip.
If your brush tip has a multitude of sharp small shapes in it, there’s a potential for lag if you use it.
I have a plethora of brush tips in my library. One of them was 100 of times worse than the original pencil brush related to this thread. It gave me a totally unbearable drawing performance.
Selecting the brush tip alone, leads to constant freezes intervals, even without drawing on the canvas. It behaves like if you were painting with a giant brush(about 3000 pixels so you can guess the speed) except that you’re not painting at all, and brush size is only about 100 pixels.
I really don’t know why it did that.
But maybe an investigation into this could lead to critical performance improvement.
I have no idea.
If you’re curious, let me know, and I’ll export the brush tip.
All you’ll have to do next, is to replace the pencil brush tip with the new one I would upload once requested.