This is maybe more a feature request. 
You cannot configure the circular scrolling in the xfce4-settings AND not in the xorg.conf-files, because it seems xfce4-settings overwrites the xorg.conf-files? I mean the applied settings, not within the files.

So I would like to see the circular scrolling configuration ability in the xfce4-settings.

This were a checkbox to activate it and probably also a drop-down-menu for the where to start scrolling.

KDE does have this feature, too, maybe have a look there, if this is wanted.