The fourth picture in Newegg website of the 2nd NIC shows a Yottamark sticker at the back. Perhaps you can still check the authencity of it with the Yottamark website.
You don't have to disable the Realtek on-board NIC unless there is some conflict either in interrupts or using the same PCIe lane as the add-on Intel NIC card(s).
One reason to keep it enabled is to see whether you can make a passthrough of the Realtek onboard NIC to a VM in ESXi work. But of course, PCIe passthrough does have plenty of complications. Don't know whether the Realtek chip supports PCIe passthrough, and whether the Aurora R4 motherboard supports PCIe passthrough; or if it is sharing PCIe lanes with other devices.