Can different units all move at their highest speed when selected together?

It seems when ranged units will have a short movement speed penalty when engaged in melee (Please correct me if I am wrong).

Consider this scenario:

I have a bunch of dragoons and there is a cuirass blob charging at me. I fired a few volley and start moving away. However, if one of the cuirassier manages to land one melee attack on one of my dragoon, the entire group slows down.

Is there a way to work around this or I have to wait and see what they are doing with the definitive edition?