C4.1 Rear inboard ball stud camber link question
 

What effect does moving this either up or down have on the car and why?

Neil

A quick look at jq the Guide, (if the same thing can be applyed to the c4 than this is what happens).

Lowering the link on the tower, will give the car more steering, as the rear will start sliding more in corners as you turn. It will also square up better when accelerating out of corners. Raising the link on the tower will add traction and reduce steering.
Lowering the complete link gives more traction, but the car seems to maintain more steering, than when lengthening the link.

Again, the further in the link is on the tower, the more stable and consistent the car feels, the further out it is, the more non-liner and and inconsistent it feels. The car will roll less and have less overall traction.