Hey Reece, so the main pressure on the grip of the bat should be through your first finger and thumb. You don’t want the other fingers to be gripping to tightly, they should be more relaxed. This adds control and allows you to have a good control of the bat angle etc.
With the sound, the too players have very good timing and hit the ball right at the peak and with very high acceleration through the ball which causes this nice sound. The often don’t really hit flatter but they hit with more power and its about the timing and acceleration more so as I mentioned.
Also especially on the short play the fingers and thumb are important, you should use them to slightly squeeze the bat as you contact on short play,pushes and also serves, this adds control and stability and gives you a closer feeling for the ball and the touch as you contact.
If you can work on a good back swing and timing this will increase the shot quality and you will get closer to this type of sound as you hit the ball 🙂
