Using LSI 2308 in PCIE x1 mode, what will I lose?

The full-height PCIe adapter slots are located on the left side of the expansion node and are numbered 1 and 2

height, double-width, x16 PCIe card All three models support an IO The PCIe slot will physically accommodate up to a x16 PCIe card

pcie 4 card in pcie 3 slot slots with maybe half-height cards? Do you know of any such thing? Edit: Maybe something like this: RC27332X16C15 2U 2-slot PCIE X16

pcie slot width PCIe Gen3 x4 PCIe slot to SFF-8644 Passive Adapter Quick View Part #:, PCI-AD The adapter comes with an adjustable 15mm tool-less fixture and full-height