>>106304738
MSI B850 Gaming Plus WiFi only has one Gen 5 x4 M.2 slot, unlike the three provided in the B850 Strix-E.
There's no need for the Gen 5 x16 lane to be split into x8 under that board config.
Learn how to shop for motherboards and how to properly read their spec sheets.
https://www.msi.com/Motherboard/B850-GAMING-PLUS-WIFI/Specification

The pic shows AMD's PCIe specs for each AM5 chipset, the boards with the main x16 lane having bifurcation issues exceed those electrical specs.
https://www.amd.com/en/products/processors/chipsets/am5.html