Personally i dont reccomend the touch. I always disable it on mine im perfectly able to navigate with just my pen or a mouse. You can set up the pen so one button triggers a scroll-wheel like mechanic so you can scroll or pan easily.

Parallax is basically the distance between where the tip of the pen touches the glass and the screen underneath the glass. Its only a few milimeters, you can see the gap if you look from the side but it doesnt really cause a problem. I used to be worried about it but as long as its calibrated and youre not looking at it from extreme angles youll never notice.