I've fixed it on my end now. Now both drives are getting the full write speed instead of just the one that was on the Chipset.
I can't tell you exactly what fixed it but here is what I did.
I've been having audio popping issues on all sound devices. Realtek onboard, and two external dacs.
In the process of trying to fix that issue. I formatted and when I installed windows I made sure the bios was set to UEFI only. Not UEFI + CSM.
I'm on the latest chipset drivers for the x570 (1.09.27.1033).
I'm switched off the ABBA bios to go back to what I knew worked (AB). I was getting random crashes with ABBA on the MSI board.
Here may be the most important part, not sure. I noticed huge DPC latency spikes. Switching off the Ryzen Balanced Power Plan to windows balanced got rid of most of the DPC latency spikes and crazy popping in audio. (I feel like it is still there but much more rare now)
I then read about turning off AMD Cool N Quiet. I did that to help with DPC latency.
I then switched to the AMD Ryzen High Performance power plan. That happens to be when I tested the SSD's again.
With most of the audio popping gone and the SSDs at full speed now. I really don't want to touch anything else.
I may be able to turn AMD Cool N Quiet back on but i'm not sure I want to.
Maybe the Link state power management has something to do with it? In power settings? Not sure.
TLDR: UEFI only when installing windows. Windows Balanced Power Plan, or Ryzen High Performance power plan. Newest x570 chipset drivers.