Francis great video. I see exactly what you are asking now. I don’t think either way is correct. Hold your initial embouchure setting. This looks great. Now move the aperture corners inwards by doing the opposite of your second method. No need to drop jaw. In your second method you are moving the aperture corners outwards towards a smile. Do the opposite of a smile. After you set the embouchure with Gregs mmmmrrrrrooooo hold it. Try to feel were the corners of the aperture are. Close your eyes. Feel where the lip corners touch. Now try to move them inwards. Another way to feel and see this is to use your finger tips to touch the aperture corners. Use one finger on your left hand and touch the left aperture corner. Do the same with your right hand. You will see that when you do your first method dropping jaw your finger tips don’t move and when you do your second method they move outwards. When you do it correctly you will see the finger tips move inwards towards each other. Hope this makes sense and helps.