It’s two Btrfs RAID0 volumes with the options in this post: (Optimizing plotting on an AMD Ryzen 5950x (or any other 16c/32t CPU) - #108 by Harris)
2x 1.2TB P3600 - temp1 (25% of the writes)
2x 1TB 970 PRO - temp2 (75% of the writes)
The 970 PROs perform slightly better (for these workloads) but it is wiser to swap the temps around because the P3600 has 6 times the endurance of the 970 PRO so the P3600 should be doing 75% of the writes. This increases the time to 1083.08 secs which equates to ~80 plots a day (yes, it’s crazy that a 16 second difference produces an extra plot a day because 16*81=1296 seconds which is enough extra time for one full plot!).
There is probably room for improvement here as I have simply shoehorned madMAx into my classic “parallel” chiapos setup with no additional tweaking.