SATA SSD vs PCIe SSD - What's the difference?

Generally speaking, if you install an SSD in the chipset slot, you're going to see it use 2 lanes worth of bandwidth most of the time

However, there's only x2 and x4 lanes accessible when using a form factor with the PCIe bus which translates to a maximum transfer speed of up to 4GBs Is

m2 slot pc PCIe Size and Lanes · PCIe x1: a single PCIe lane does not support the interface] · PCIe x4: NVMe SSDs occupy a single x4 slot] · PCIe x8: expansion cards

m24 slot wallet I bought the adata drive knowing that both slots support pcie x4 This is really frustrating since I expected at least 2900 read speed 0