Just wanted to add comment on Batch 2 Z9 minis.
My batch 2 Z9 minis (arrived today) have the drop down box to choose frequency. It has all the same frequencies as my batch 1 Z9 mini.
The only issue is that they are not steady when overclocking to 700 frequency like batch 1. The highest they will go without pooping out is 668 frequency.
Mine is running fine at 675. I also tried 700 and it ran for a few minutes and then one single board would stop completely. My temp at 61C and getting 14.9 average