NVMe drives are kinda like SATA drives in terms of broad general compatibility. Your board is PCIe 3.0, so you only need 3.0 performance. You can install a 4.0 drive if you want, but it will run in 3.0 mode/speed. Any NVMe 3.0 x4 drive from a reputable brand should work well. For a desktop system, you typically use 2280 drives (22mm wide x 80mm long), and M key (refers to the position of the slot cut in the edge connector).
Personally, for a PCIe 3.0 system, I would go for a Seagate Firecuda 510 or a WD_BLACK SN750, or they both have more budget oriented drives if those performance gaming models are more than you want to spend. Samsung also have an extremely good rep for SSDs, and their 970 NVMe drives are high performing 3.0 units. Crucial are worth a look too, since Micron make the actual silicon. There are many others out there, there's a huge choice when it comes to NVMe drives. I have a bias towards the traditional storage vendors like Seagate and WD, but that's just me.
NVMe 3.0 x4 slots are up to 4 GB/s, and typical high performance 3.0 NVMe drives are somewhere in the 3000 MB/s and above range, with more general ones in the 1000 MB/s upwards range. Just about any good NVMe drive that's being sold today will be a big improvement over SATA, which is up to 6 Gb/s / 600 MB/s (it's a 10 bit code for 8 bits of data).
Edit: also you'll find both NVMe and PCIe used to describe them. NVMe is essentially a special type of PCIe for non-volatile memory storage.
