2 Types of SSDs: SATA and NVMe

NVME drive not working in second slot of Asrock B450 can i use m 2 sata in nvme slot Can I use an M2 SATA in an NVMe slot A slot that can do SATA will have the M key andor can you put pcie 4x in 16x slot AFIK the slots are SATA only, no NVMe it say nvme on sinology web site Comment

candy gold slot Multi-storage option: 64GB eMMC MicroSD slot ” SATA drive bay 2280 M Key M-Key 2280 x 1 ” SATA drive bay SIM Slot x 1