NGFF stands for “Next Generation Form Factor” and is a compact M.2 SSD that is connected via SATA. Data transfer rates of up to 6Gb/s can be achieved here, depending on the hardware environment. M.2 NGFF is a cheaper solution compared to the M.2 NVMe SSD, which is connected via PCIe.
NVME stands for “Non-Volatile Memory Express” and offers the full speed advantage over NGFF because they are connected via PCIe and use the NVMe protocol for data transfer, which is many times faster. To be able to use these fast transfer rates, you need a case with an M.2 interface that supports PCIe. Like for example the GRAUGEAR G-M201-AC-10G. Connected to appropriate hardware, data transfer rates of up to 10Gb/s can be achieved.