I haven't tried the dynamic option yet; I'm just happy to be functional.
I spent the day playing with various hardware configurations using my mini-itx machine. It was my 9700K causing the problems. It ran on my mini-itx board without any modifications (which had a 9900K in it as a mini server). So, I started swapping components from the z390-i to the z390-e. RAM... still froze. That only left CPU or mobo. So I swapped the 9900K in to z390-e and was off to the races. I set it up as the iMac19,1 using the iGPU and haven't had any trouble since. I adjusted my fans in the BIOS, added the AI-overclock, and haven't seen any problems in the last three hours. I've hit it with geekbench, cinebench, valley, etc. Hackintool seems quite pleased and recognizes everything well.
I assume it's just this specific 9700K, but I've had it in various builds throughout the last year and didn't think it had problems. I even had it running a mojave build at one point - but I didn't use it much because... it was freezing. Derp.
So it seems like everyone has been correct. Running the latest kexts does seem to work great with the 5700XT. I just had a bad proc.