Anyone else spending more time, looking for pictures to draw then practicing drawing? Any insights? is there a Proko reference pack of images to practice line weights?

Are there any examples of artists doing two methods or even all 3 methods of using line weight (1. outline, 2. show depth, 3. to show light and dark areas) at the same time, i.e. in the same piece? or is this a decision that is made before and then carried through to the end of each piece? Is it common for artists to switch line weight usage, for different pieces? (1 project, line weight is for light/dark, 1 project for depth?)