You are correct that the camber is set at the factory, there are ways to tweek it but ive yet to see the need.
Ive lowered my car, by cutting the springs, mostly to adjust the rear sag that had developed, as i wanted the nose to point straight and not upward to the big dipper. I am happy with it and like the handling better. I have had numerous suspension, and steering parts replaced by myself. The 740 is very straight forward. I have found it easier for me to do my own alignments. I can align it fairly quickly. My method is to take two jack stands, place them along side the car. tie a thin string to the jack so that the string runs along side each rim. Adjust the jack height so its the same height as the center hub of the front and back. Then measuring at four points (The lip of the rim back and front). It takes a little adjusting of the jacks to get them straight with the car. measure adjust measure adjust the trick is to get the rear rim measurements exactly the same and the front close, as the front varies depending on toe in or toe out in the adjust the wheel in or out.

That is my basic method there's more to it but that's how i get it adjusted and I can do it after any modifications to the steering or suspension. I often check it on routine maintenance. Of course the car has to be pointed straight. and the steering column locked, done on a flat surface, and repeat process on other side. Make sure all steering and suspension parts are not worn.

If the car has ever been hit as to disturb the geometry of the rear axle this method will not work.