I have a Surface, it works reasonably well for the same task. But the same applies - it is not "pretty" svg graphics, but faster and easier. I suppose you could always make the initial diagram this way, and create it in a 2d cad like program if you need to.

Does it have some sort of grid-layout so you can just draw linear sections etc.?

Is there any other case where prettification works better? (Splines, I suppose).

I haven't really searched for a program like that, and rather used it as a an electronic piece of paper.