I asked exactly the same question 4 years ago and since then I do run into the same problem:

When using water color and low pressure the lines are jagged. See picture. I changed the settings as described in your help / FAQ but nothing worked. This problems ONLY occurred with water color and low pressure (especially delicate on dry) and (until I find more), so it does not seem to be a general problem of the settings. I also tested it with 74 dpi up to 300 dpi, no change.

Click image for larger version. 

Name:	Noname.jpg 
Views:	211 
Size:	265.4 KB 
ID:	95146

My tablet an Intuos, my system is WIN 10.

Besides my hope that you know how to get rid of this problems, am I the only one who has such problems? Can you reproduce it?

Thanks in advance!