I know this thread is old, but I solved this problem mathematically, so I believe it can be very helpful for everyone.
Function
This function takes inputs of a Spline, Segments, and Radius to calculate and draw a circle along the Spline.
In order to fit the content into one screenshot, I used two Math Expressions.
(360 - (360 / vSegments))
(4 * (tan(((D2R((360 / vSegments))) / 4))))
Preview
10 Segments
4 Segments
3 Segments
2 Segments
The computed values may be very large, which can be influenced by floating-point precision and may result in the circle appearing slightly more like an ellipse.
