Which Slot Should You Use?

So I have a bit of confusion here on which Slot do I use Motherboard manual says following -For 3rd gen AMD Ryzen Processors, the _1 supports PCIe

2 is a specification for internal expansion cards on PC mainboards and notebook computers 1 x 67 pin key M slot 1 x 67 pin key B slot (

m2 slot screw An slot is a type of expansion slot found on modern motherboards that is primarily used for connecting solid-state drives

m2 slot Why not a mix of NVMe + SATA III SSD? Add in cards to go in an empty PCIe slot 1 or 2 drives in one of those