When drawing a rounded retangle, I find that the stroke line is alyways thicker than what it should be.
For example: I set stroke 1 pixel soft, I see 2 pixels thick line, however the corner is about exactly 1 pixel, but this make the stroke like look unbalance and not nice
If you want a single pixel line, try 1-pixel hard.
That will make the line exactly 1 pixel. However, another problem arise, the corners look really bad.