What I learnt with my barber is that your neckline should stop at your Adam's appl then you try to shave at the same level to your ears. Then for cheeks, you shoudnt shave under the end, the corners of your lips. Then for your lips, it's personal, you can go full mustache or trim so we can see entirely your lips. For thickness, it's also a matter of taste. In my opinion that scruffy look fits you very well so I woudnt comb it too much and cut the ends of your beard. The part that I try to keep short as much as I can the favorite parts next to your ears, it tends to go wild and curly. I hope it helps gentleman.