ASTs installed a short while ago, here's the results. Running AST Springs with Macht Schnell Competition Wheel spacers. This confirms the 30mm front/15mm rear drop listed in OP, also no rubbing with spacers.
Very happy with the new ride height, these springs are right on the money.
Vehicle 2021 BMW M3 Competition
Wheels
F: 275/35-19 Prielli Zero
R: 285/30-20 Pirelli Zero
Height (OEM)
DF: 63.9cm PF: 63.5cm
DR: 63.8cm PR: 63.4cm
Height (AST)
DF: 60.9cm PF: 60.7cm
DR: 62.2cm PR: 61.6cm
Drop Height
F: 30mm/28mm (30mm)
R: 16mm/18mm (15mm)
Spacers
F: Macht Schnell Competition Wheel Spacers - 12mm
R: Macht Schnell Competition Wheel Spacers - 10mm