Here is a quick example of how this could be done.
I used nested L1S as a segment to distribute through A2S (for better surface distribution).
FP is simple gravel preset generated on Surface (Plane001) + Area Spline set as Excule (Line001). The width for removing the gravel segments is controlled by the Thickness (calculating from the center of the spline).
RC is driven by the same Spline (Line001) and the same Surface (Plane001). I have exposed the "X-fixed size" parameter for the Path width. It is also calculated from the center so basically, it is half-size, but I used this method so you enter the same value both for RC and FP.
You could also use RC object as an Exclude object for FP area so you don't need a spline to exclude the option but depending on the RC object this method could produce some issues.
Sorry, I don't have any more time to elaborate, I`m on a deadline project at the moment.
here is a link for the scene file:https://we.tl/t-01N4vXexhm