function setupRadiusElement(); ... Would this be possible?

[redchair218]

I wonder as to whether it is simply possible to copy one of the other functions to address radii of circleMarkers? Right now, if initial conditions are set well enough, you can adjust the width of the border to make the circle bigger. However, given its current form, you can not separate the fillColor from the color within the styling.

Here's a demo of circleMarkers in use with styleEditor ... https://jsfiddle.net/redchair218/x76jzLys/3/