9-11...
Bending the wrist does indeed help you slice the ball more, but you should really incorporate it into the topspin/slice serve, which is a combination of both, not one or the other.
Try to use the same grip for all serves. Why? Because you can lessen one more thing which increases error chances. Grip changes cannot always be accurate, and when you S/V, especially off your slower second serve, you need an EXACT, replicable grip.
Most players employ full pronation on the first flat serves.
But on second serves, some just lead with the edge of the racket for more rackethead speed, on their top/slice second serves. You can pronate some, but you have to limit it somewhat to get consistent slice or spin.
For twist serves, you can pronate some also, but some choose instead to just slice upwards at the ball leading with the edge of the racket, never fully exposing the face to the ball.