PCIe x16 GPU card into a PCIe x8 slot?

PCIe x16: This is the largest PCIe slot with 16 data lanes PCIe x16 slots are associated with graphics cards and provide the highest bandwidth

2 Use larger SSDs, and manually partition them to do double-duty as SLOG and a small separate pool You'll get the separate pool you want, but

pcie 1 slot In ASUS 「PCIe x16 Slots - 7」

pci slot meaning PCI Express