Same 64 images. Exported to JPG. 100% quality.

Lightroom 6 on i5 – 80 seconds – 16 gigs of ram.
Lightroom Classic CC on M1 – 32 seconds – 8 gigs of ram. Intel version of Lightroom Classic

Did another test with a different set of photos

Lightroom 6 on i5 – 4 minutes 52 seconds – 167 photos
Lightroom Classic CC on M1 – 2 minutes 18 seconds – 167 photos