Just got the mail back from the support:
After check, it [ASRock X570D4I-2T] can support x16, x8x8, x8x4x4, x4x4x4x4. J"
I still want to know if the Oculink can be broken out to 4x PCIe or if it's just SATA.
Edit: Only one M.2 makes me sad