2002 Avalon has a high pitch squeal that goes away when brakes are applied. Rotors and pads replaced but squeal remains.
You may have a caliper that is not fully releasing when your foot comes off the pedal. Try carefully touching the metal wheels with your finger after driving for a few miles to see if one is hotter than the others. If it is then that wheel’s brake caliper is dragging and needs to be repaired.
It could also be a wheel bearing going bad.