camber arms all on front have been said to slip on the odd occasion.
rear camber arms are screw in/out so they cant slip.

front extended ball joints are also just to replace ur old worn out ones.
i think you can get offset ball joints for the front that will give u that camber. but its not controlled. just go low and determine if u really want more. for street the act of lowering it will give it about as much camber as you will need. unless u want a stanced look.

squeeking is commonly associated to trailing arm bushings or maybe Rear LCA bushes or squeeky shocks.

imo organise as many bushings as you can, then worry about coilovers, your coils might just come to life with the rectified rubber making your car more comfortable and more predictable/sporty

PS: rear camber arms will replace one Rubber bushing straight away so thats why i suggested rear