Vx or Vy indicated speeds are not affected by wind, the angle or flight path in relation to the earths surface will change with wind.
The best lift drag speed gives optimum glide distance or the best rate of climb performance, gliders do use polar charts or glide computers on the vario/vsi to obtain the best wind penetration glide speed to cover the greatest distance in the shortest time with least loss of altitude or another way the optimum flight path.
The same principle as the best lift drag speed indicator on the PFD.