If I use a brake on a non machined anodized surface will it make that screeching sound? Will the black streak left behind be very noticeable on a black wheel?
No. Machined sidewalls are a recent phenomenon. We used brakes on anodized, non-machined sidewalls for decades and it worked fine. If your brakes are squealing it's probably a shoe toe-in issue. And black streaks on a black anodized sidewall are not noticeable at distances greater than 6 inches.