Do props come perfectly tuned and balanced from the factory, or are the tolerances of mass production loose enough that almost any prop would benefit from a tune even when brand new?

No and basically no 2 props are the exact same as being labeled the same model, diameter and pitch. There is a certain amount of handling, temperature, curing, hand finishing and final finish that can vary from prop to prop during manufacturing from start to end. Also some added info at one time Mercruiser / Mercury Racing even had a Service Bulletin about stamped pitch on the props versus true pitch differences.

No, not perfect. They are "within specs"

Those are the answers that I was pretty much expecting. Thanks!

There are a number of reasons the box stock propellers have variations in out of the box new form.

One of the biggest issues in my opinion is balance. Stock props are balanced prior to the polishing method of drag finishing. Because of this, it is rare to have a perfectly balanced propeller out of the box. This is why we high polish all our polised requests by hand.

Brett