How to Trace 101

If it was good enough for Norman Rockwell here, it's good enough for you. He used an opaque projector. If he had modern software you can bet your artist beret and black turtleneck this would all be on layers.
NOTE
Now he did study art the old timey way. He also didn't copy his photos one to one. He changed things as the piece needed. It wasn't a shortcut to improvement like what Josh is always asking for. It was a shortcut to photorealism without spending months or even years on it like the old masters had to.
Dude had a weekly deadline. Michelangelo had a degenerate Pope with a PR campaign and endless money.
As for using tracing for study
It is simply one tool in the kit that can help. ONE TOOL. Like building a house. Using only hammers will result in a shitty house. Using Poser only will result in shitty art. Using only DeviantArt/ Pintrest pose resources will do the same.
Truth be: If you don't already have good grasp on these things, on your own you probably won't know what it is that works about what you're tracing. Having someone, say, a teacher or even a YouTube influencer, explain what the circles and tubes in @Lensing's example up above represent, will be invaluable.
But you still need to put in the work to learn how to take what they tell you and apply it on demand.