How to set caster?

Not sure what you mean with "then you will lose some"..?

How does the cam move the upper control arm forward or backward? (to increasing or decreasing caster). Is it as simple as undoing the bolt (the one on the left side in the picture) on the one side and turning the stud on the other side of each upper control arm bracket to make it move.

I'm just struggling to understand how these cams work exactly.