2 questions about Open Contours

Now that I have successfully enabled & created open contours, how do I change the width of their strokes?
Also, how do I turn the strokes into filled shapes, e.g. turning 1 stroked circle into the equivalent of the union of 2 concentric circles?

The width can’t be changed right now.

To achieve a union of two overlapping circles, it is easiest to make such circles in a normal font (with help of the union feature), and then copy and paste them into the single stroke font.