The car will have a slightly stiffer ride because it is lowered but will handle better in the corners. Take it for a test drive and make sure it does not bottom out when you hit slight bumps. This might be the start of the struts and shocks failing due to the shorter travel length of the springs. A leaking strut is also an early sign of this. I recommend CC plates when lowering but it isn't absolutely necessary. Just make sure the alignment is right or your front tires will wear alot faster. Also, because the
suspension is now stiffer from the springs, you may experience more chassis shake. See if the car has subframes on it. It'll help stiffen the chassis and get the front and rear working more in tune through the corners instead of the tail always wanting to come loose. Hope this helps.