If you purchase the plans, and get access to the forum, you'll see that almost all of the newer builds use rack and pinion, and many of the early leadscrew machines have been converted. Rach and pinion is much more efficient than acme leadscrews, and will give 2-3x better performance.
If you want to use screw drive, then you'd want to use 20-25mm diameter screws with a 10-25mm pitch.