I have to set this up whenever I install Clip. Go to File>>>Preferences>>>Tablet and toggle from Wintab to TabletPC and save. Then be sure to adjust your pen pressure settings under File>>> Pen Pressure Settings.
I also recommend you configure your sensitivity in the Surface app for your pen.
My other tip is to adjust the Stabilization setting on the individual pens you ink and paint with (located in the Tool Property Menu for that tool) until you get the right feel. Dialing that in helps with the N-Trig jitters and with lag on your brushes and pens!