These are fantastic! I guess the question I would ask is, where does the instructor begin? What I would do, is find a reference that I want to draw, then I'd actually open the tutorial video (or videos) and follow the steps, but not the instructor's reference or drawing. That way, you can start to get an idea of the instructor's method and process, then implement them to your own art and style. I think this would be an interesting exercise and help you understand if you're referencing the instructor's artwork, or the actual image. Again, these drawings are excellent! I'm sure you'll figure out your best process of drawing from reference. I hope this helps.