Also highly recommend https://www.proko.com/ (particularly "Figure Drawing Fundamentals") and https://drawabox.com/. I didn't realize how much structure drawing has, and both of those describe it in a way that's good for my right-brain. I'll never be a great artist, but it's still fun to draw!
I never tried "structured" drawing before. I think it's a sort of different skill. But I think it's also how you really start to unlock the ability to draw from imagination (without a reference).
Drawing from sight will moreso change the way you view the world (in terms of light and shadow and the shapes those make). Similar to photography.
