The chopping/grip advice is missing a critical component: your two farthest forward knuckles on your non-knife hand should be contacting the knife blade at all times. This gives you precise control and you know exactly where the cutting surface is. It takes a lot of practice to do properly, but that is how the pros do it. I recommend this video from Jacques Pepin for an example: youtu.be/nffGuGwCE3E