@markterreau said:
Where can a guy find the aforementioned BZ_Spline tools?
In the Extension Store: https://sketchucation.com/pluginstore?pln=BezierSpline
Best would be to install the Sketchucation Extension Store tool under Resources at the top of this page. Then use it to install extensions hosted here.
There's also FredoSpline which has more options than the older Bezier Spline.