I've had two PTs lowered with Eibach springs (1.6 front, 2 back) and haven't needed the camber kit. Some do, most don't. Your cornering will improve to a point, but you'll still need better sway bars,Tokico shocks, poly bushings and a front strut bar. If you are made of money
then some wider tires would be nice, too, but if you are keeping it on the sane side then just springs will be nice.