can rear camber be adjusted without affecting tow?
 

I need to adjust the camber on the rear wheels of my 930, and have a tool that will give me pretty precise vertical angle measurements. If I change camber, would that also affect toe, or are those two independent?

It will affect toe.

It will affect toe because you have to loosen all the bolts that attach the trailing arm to the spring plate so the trailing arm can be rotated while adjusting camber. Use a sharpie to scribe or mark the position of the mounting bolts where they go through the spring plate and trailing arm before loosening them.

If the original old semi compressed rubber bushings are still in the trailing arms where they mount to the cross member then they like to stay in the same position they were in so camber may not change much but it's easy to measure the distance from somewhere on the brake caliper to the torsion bar cover and keep that distance the same when tightening the trailing arm to spring plate bolts. That will keep toe the same or real close to where it was.
For a street car the rears should be toed in about 1/32" on each side when the car is settled on the ground.
Use a torque wrench on those bolts and don't over tighten them. I don't remember the torque spec.