Calipers: Big one or lightweight?

[Humble]

I think, realistically for a beetle, a ~12" (~300mm) vented rotor is about the biggest rotor you would need. 10-11" would be about perfect. For calipers, lightweight 4-pots would be best, but even 2-pot on each corner would be fine. Matching the calipers to the MC would be the biggest challenge if you choose to mix and match from different manufacturers. Another thing to consider is consumables like brake pads, high end calipers may need specific non-standard pads.

Going with a wilwood 4-pot 11" setup similar to a miata would be a great starting point and you would still be able to use 15" wheels (the best for cheap, sticky tires). My second suggestion would be a 944 turbo setup (12" rotors, 4-pots) with a 911/930 MC, with easier to find parts, possibly cheaper too.