constant velocity, as the name implies, moves the tool at a constant velocity, with means that it looks ahead some moves to plan the current move´s speed, think of it as if you draw a curve which is drawn in small straight segments, the tool would move in one seamless stroke along the curve. If you have exact stop turned on, then the tool would accelerate, reach the max speed, and deaccelerate on each one of those segments, which would make the cutting process take longer if you have a small acceleration value.
To sum up, CV just makes things faster but the down side is that some corners might get rounded because the machine cannot ake a tight turn and keep constant velocity.
exact stop takes longer but follows the true shape you are trying to cut.
hope this helps
Fernando