"When the PCIE 5.0 M.2 card is installed on the PCIEX16(G5)_2, PCIEX16(G5)_1 will run x8 only." It indicates that the PCIE 5.0 M.2 card will only operate at x8 speed rather than x16, regardless of whether it is put in PCIEX16(G5) 2, PCIEX16(G5) 1, or both slots.
Additionally, installing a single VGA in PCIEX16(G5) 1 will offer x16, but installing a single VGA in PCIEX16(G5) 2 will only provide x8 according to pages 1–8 of the user manual. Please refer to pages 1–12 to review the M.2 slot specs.
Could you please provide the brand and model of the SSDs you expect to install?