I had some issues with a Kamvas Pro 19 pen display where there was a small offset from where the stylus touched the screen and where the line was drawn.
I tweaked .config/kcminputrc to balance it out to where it felt comfortable for me, i.e. just under the nib.
Just something to consider, adding some input fields to easily tweak the offset?
I tried working with the system settings, but it was not very helpful. Impossible to make pixel adjustments with the controls. The calibration screen, I don’t understand how that works, because I always managed to add to the offset, and never reduce it.