The first thing that I look when a KP have these extensions on the backtrace are the CPU tray northbridge heatsink push-pins, also the northbridge diode temperature:
- com.apple.driver.AppleACPIPlatform
- com.apple.driver.AppleIntelCPUPowerManagement
Btw, did you knew that Samsung 870 EVO is not compatible with Mac Pros and known to cause several problems, like not working after a reboot or waking from sleep?
I'm afraid that going back to High Sierra will not make your Mac Pro to work as expected again, you need to diagnose it correctly.