What you are calling "camber boxes" are really called pivot boxes. Camber boxes are installed at the front of the car. The reason I make this distinction is that you don't want to use the pivot boxes to make rear camber adjustments. Their purpose is to relocate the inner pickup points based on particular geometry requirements/choices. The spring plates should be used to adjust both camber and toe. Yes, you can make camber adjustments with the pivot boxes, but you may also negatively affect the suspension geometry in the process.
Porsche created the shorter trailing arms for the mid-year 1973 RSR to better match camber gain to body roll. From what I have read here on Pelican, the RSR was not very stable in high speeds turns. So they raised the inner pickup on the Turbo to get some additional toe-in as the suspension compressed to gain some rear stability in those high speed turns. I do not believe the Turbo gained any anti-squat from this change. In fact, it may have lost some anti-squat.
My race car is built on an 1987 Turbo chassis using 930 trailing arms. The trailing arm inner and outer pickup points are raised. Here are some photos:
You don't want to raise the inner pickup point compared to the outer pickup point without a plan. Porsche did an excellent job with the 930 rear suspension geometry. The inner and outer pickup points on my car were raised about the same amount so we could lower the rear of the car a bunch, not have the roll center get too low, and keep the geometry in the proper operating range. We raised the spindles in the front for the same reason. You want the rear roll center higher than the front roll center and you want both of them above the ground.
Using the standard trailing arms, there may be something to be gained by raising the inner pickup point some on its own. If just raising the inner pickup point was such a great idea, Porsche would have just moved the pickup point up and not changed to a shorter arm for the RSR. There had to be a reason for the arm change. I would look for that reason with the modeling you are doing. I would look at toe change specifically. You want some toe in increase as the suspension compresses, but not too much. To see the differences, you will want to model the 930 trailing arm as well.
The bottom line is that the main purpose of the pivot boxes is to allow you to raise the inner pickup points of lowered cars to maintain appropriate roll centers and keep the suspension in the proper operating range.