Scissors effect can draw and erase in a slice and does not require confirmation by right-click, so you can use that instead of Draw effect.
I’ve added two experimental options to Paint and Erase effects that will probably solve your performance issue. You can set a minimum distance for mouse move events, so if your tablet generates many superfluous events, you can ignore them by setting the appropriate threshold. In addition to this, I’ve exposed a flag to enable/disable delayed paint, i.e., if you modify the segmentation immediately when you move the mouse or only when the moues button is released. This might make the performance worse, but if your computer is fast enough then you may get more rich immediate feedback during painting.
How to adjust these options? Download Slicer revision 28260 or later (should be available tomorrow). Open Python interactor (Ctrl+3) and copy-paste the code below. You can change the numbers to find a good combination that works the best for you.
paint=slicer.modules.segmenteditor.widgetRepresentation().self().editor.effectByName("Paint")
paint.delayedPaint=False
paint.minimumPaintPointDistance=3
If you find that changing these setting help then copy the code into your Slicer startup (.slicerrc) file.