PCIe NVMe SSD on PCIe slot-Worth it?

If two SSDs are installed in a “Dual NVMe PCIe adapter” and the adapter is plugged in either PCIe slot2 or slot7

Most computers and storage drives still use the common SATA or PCIe interfaces to sling your bits of data around, but if you're lucky

can you use a pcie 40 nvme in a 30 slot SATA SSDs and SSDs that use two PCI Express lanes tend to use keys B and M to maximize compatibility, since both connectors can deliver both

can i put a pcie 30 in a 40 slot PCIe x4 slot with Lower impedance CONNECTIVITY Dual NVMe PCIe * Connectors