I do a lot of guitar design. The major electric guitar brands have some very iconic shapes. A very common practice is to take an existing design as a starting place, and tweak the curves and features to make it your own. If you do a Google Image search for, "Stratocaster technical drawing," you will find a ton of images that are very simple technical outlines of the body. I save those images and open them in Illustrator. Then I use the image trace tool to convert it to a vector graphic. Unfortunately, however, it never works. No matter how many of the values I tweak in the tracing tool, I end up with a slightly scattered or skipping line drawing that is made up of hundreds of paths that do look like a shape, when viewed at 100%, but cannot be edited as a single path with anchor points and handles. I have been able to bump the faders to get a more solid outline, but it seems to be slightly off in some very important places. It's like it's trying to average too many points and paths, and ends up with a really fat (heavy stroke) path, that is simply a little wrong.
Is there some way to use the image trace tool and do something like, the high fidelity photo preset to get really close... but then do some kind of "Convert all paths to single outline" tool? I know about the "simplify path" tool, and that does work to get even closer. But, without having a single path... I can't really do any real conceptual designs.
The trouble is that Illustrator hasn't got the faintest idea what a guitar is. So no amount of automatic tracing will ever get you where you want to go. The most efficient way to do things is to become proficient with the Pen tool and learn how to nudge curves using bezier handles. That way you can trace photographs manually using very few anchor points. For smooth curves and economical positioning of anchor points, study the way type fonts are drawn. Outline some type and check out the vectors.