It would only support two nvmes in that slot unless the card you has a pcie switch (to my knowledge the asus card does not; it NEEDS bifurcation support on the motherboard)
To quote:
PCIe Bandwidth Bifurcation Configuration
[Auto] Run full PCIe X16 mode.
[X8/X8] Split up PCIEX16(G5)_1 that runs at X16 into X8/X8
Seems the slot can only do either x16 or x8x8 - no option for x4x4x4x4
No need for AI; just rtfm 