The easiest way to explain the baseplate angle is that the more angle your baseplate will have, the more it will turn. Less angle means more stability. At higher speeds you’ll want more stability so a lower angle baseplate. The lower angle will make it harder to turn, the rider will have to hang more and to get the board to turn.
Some riders even go for split angles, with more angle in the front and less in the back, to prevent steering of back truck, which is a cause of speed wobbles. If you are looking to go fast, make sure to put softer bushings in the front truck and harder in the back truck, this will help you with stability.