Even if you only have one camera, one other (small) advantage of shortcuts is that you can put a function (eg. turning off motion detection) at the top of the front page, one button, so you don’t have to dig into a menu to accomplish it.
They did not, for some reason, put sound control as one of options for shortcut actions. However, I’ll add that request to Wyze’s feature request tracker. Perhaps someday they will add it.
Turning the camera off temporarily disables streaming, stops recording to the microSD card, stops all alerts/notifications, etc. Restart on the other hand is a reboot of the firmware, same as if you unplugged and replugged the camera.
If you are not hearing sound, make sure (of course) that your phone volume is turned up and make sure the Wyze app has the appropriate permissions. Check the troubleshooting guide found under Support at the top of this page. If that doesn’t fix it, you should file a support ticket from within the app.