Quick follow-up:
Regarding brake squeel I tried the hard braking from high speed, as someone mentioned earlier in this thread, to help re-seat the brake pads — it did help a bit. Now the rear seems to squeak more than the front.
I'm also getting a light metallic/squeaky noise when rolling off the throttle — kind of like a faint brake squeal or a tiny bird chirp

. It disappears instantly when I apply little throttle or pull the clutch.
I first thought it might be the brake pads lightly touching the disc, or maybe something in the drivetrain like the shaft relaxing under engine braking.
Tried lightly braking while riding, but the sound didn’t really change.
Unfortunately, I still can’t clearly identify where this new sound is coming from. Could be drivetrain, could still be brakes — not sure yet.