BRUSH LAG WHEN USING INTUOS PRO PAPER! PLEASE HELP!

I just got a new Intuos Pro Paper Edition about a week ago and I have noticed (hard not to) that whenever I use any brush, even untextured ones, I get a HUGE slowdown on photoshop - it's almost as if my photoshop gets completely frozen. My computer is a Surface Pro 3 and I get NO LAGS when using the Stylus on Photoshop. The lag comes only when I plug in the tablet ( I also use a big monitor)

     What happens:

     - Delay when using any brush (smudge tool, mix brush, brush tool etc). Sometimes it takes about 1 minute for the stroke to appear. In the meanwhile I can't even use      photoshop because of the crash;

     - Photoshop crashes or slows down when I Ctrl+Z a stroke;

     - Photoshop slows down when using "liquify" tool;

     - Any action in Photoshop just takes too long.

     What I have tried ( but didn't solve the issue):

     - Edit > Preferences > Performance > Let Photoshop use 85% (it used to be around 40%) and then "History States 40" (it was around 20-30)

     - Edit > Preferences > Performance >  Scratch Discs;

    - Restarted photoshop and PC;

     - Some people reported they get lag when sketching with the "rulers" activated, but I don't have them on and still get the lag;

     - Just updated Photoshop CC 2017 to CC 2018 with hopes to solve the issue;

     - Created smaller files and tried to work with fewer layers in order to reduce the lag;

     - I have NOT reinstalled the tablet driver as I noticed that many people got no improvements in doing so.

    My computer specs:

     Surface Pro 3

     Processor: Intel Core i7 1.70GHz 2.30

     Ram 8.00 GB

IF ANYONE COULD HELP ME I WOULD BE MOST THANKFUL AS THIS PROBLEM IS DRIVING ME CRAZY

THANKS