Both the Z590 Hero and the Z590-I have the option to set PCIe slot 1 (top slot) to allow the Hyper X16 card to work. But there is a catch unfortunately: In it states that "you will only be able to see three of the drives" on the Hyper X16. This means it only uses 12 of the 16 lanes on that slot. I can only assume you can mix in the onboard M.2 slot as the fourth drive. I am assuming as I did not test this.
In order to get the PCH raid menu to pop up I put an Optane drive in the M.2 slot and proceeded to try and setup a three drive raid in bios, this was not possible, it saw the Optane and enabled the RAID but did not allow the Sabrent drives to be added to the RAID. Windows sees the three drives on the Hyper AIC as three separate drives where you can win raid or softraid them without issues.
I will circle back with all Optanes drives to enable booting to the Hyper AIC, I am kinda bummed it can only see three of the four drives but I will try the onboard M.2 again as the fourth drive. I assume this is for use of eight lanes on the M.2 slots. I noticed some SATA port lanes being re provisioned when I was disabling devices in BIOS. I wanted to be able to boot on the Hyper AIC using all four third party Gen4 drives.