If your disc rotor warped, the most significant thing will be brake pedal rejection. As you hit the brakes, your feet will feel numb/shakey from the force feedback from uneven rotor surface.

Distinctive screeching sound could be as follow:

1. Uneven disc rotor - but you'll get to feel it with your feet. If your feet doesn't get any feedback from the pedal, which means it's not. Even if there's uneven, it should be totally negligible.
2. Disc cover bent and hit your rotor. Refer picture below:
   
3. If you have just recently changed to new pad, suddenly these type of distinctive screeching sound appear, it could be your rotor being grind off too much, left a sharp edge that causes brake pad grinding noise. Usually it takes a Genting hard driving to grind in your new pad, so it fit your rotor.
   
4. The new brake pad working temperature sohigh

I usually stick to BOSCH pads, street use spec, many dust but does very little harm to rotor. Performance, just barely suffice my usual short spiritual driving. My brake pads usually lasted me atleast 30k km, unless I go Genting often. If I go track"ing", will hook up a pair of local made MINTYE pads, it's cheap, noisy but reasonable braking performance street use pad.

On wheel brake rotor skim usually RM35/side. Off wheel skim usually RM50/side. On wheel skimming will have better accuracy since bearing movement is included. Off wheel skimming will have maximum flat surface, absolutely glass effect after skim. CK case could be discounted price. If figured the brake rotor bent too much, might as well change to a new unit. Funker Choy is selling his racing rotor away I heard Can fit Persona/Gen2.

Minthye too much asbestors, compound too hard alas the screeching sound despite not hitting the brake pedal. It is very normal geh. Again like I said, it's cheap and powderful pads they produce, and using it consecutively, your rotor will be gone sooner.