Only use one flag for toggling to beziers

previously there were individual toggles for
smoothed and linear segments, because I wanted
to see both simultaneously for debugging. This isn't
a useful case for production, and it's nicer to have
just one switch, "drawBezierCurves"
Add a switch for variable/fixed stroke width

The variable stroke width stuff is janky at best, so turn it off by
default and let the user turn it on