Dit, you have it backwards w.r.t. min drag and min power vs best range and best endurance. You wrote
...L/Dmax allows the aircraft to operate at it's most efficient in regards to time (in regards to distance you want Vminpower which is a different speed...
In a
piston aircraft best *range* ie most distance per unit of fuel occurs at the tangent to the power curve, the speed for which also corresponds to minimum drag. Best *endurance* ie most time per unit of fuel corresponds to minimum power.