Need some advice on rear suspension setup

I need some help with my rear suspension set up for a 2014 GT. Previous owner put eibach sportline springs on it and nothing else. I'm doing camber bolts and a Whiteline Panhard bar. Whats the deal with needing the lower and upper control arm(s)? If I do an adjustable on the upper, do I need adjustables in the lowers, and vice versa? If I have to realign the rear end, why would I need adjustability in both upper and lower arms?
And whats the deal with the LCA relo brackets? Do I really need these with the car lowered as per eibach sportline specs? I'm not professionally dragging or autocrossing the car. I just want the mechanics of the car to be correct and for it to hook up well.
 
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