Before a Circle is drawn its line width and color can be set. For Filled Circles, the color can be set. The Circle Line Width field is a scaled dimension in inches if >0. If 0 it is a 1 pixel wide line at all zooms. If the value is negative, it is a scale-independent number of pixels wide.

Circles and Filled Circles are created by selecting either the center position or a point on the edge of the circle and dragging to specify the radius.

Draw Circle from Tangent. Draw a Circle from the Edge.
Draw Circle from Center. Draw a Circle from the Center.
Draw Filled Circle from Tangent. Draw a Filled Circle from the Edge.
Draw Filled Circle from Center. Draw a Filled Circle from the Center.