Crucial MX500 M2 SSD

When I was researching parts for my new ASUS TUF H370-Pro Gaming motherboard to do this: Custom Computer Build I read in the specifications this:

Storage:

32GB/s M.2 1x M.2 2242-2280 (SATA+PCIe 3.0 x2)  

1 x M.2 2232-22110 (PCIe 3.0x4)...

Hummmm, onboard SSD? How nice! Maybe, maybe not! So now I need to do some more research and this will be (hopefully) my boot device and this is what I found:

Crucial MX500 500GB 3D NAND SATA M.2 Type 2280SS Internal SSD - CT500MX500SSD4

Notice in the specification for the H370 SATA and/or PCIe, this will lead me to do more research once I have the product installed on the motherboard (did you see the part where it said: READ all the documentation? Well ya... DUH!)

Specifications:

• Compatible Devices: Any that accepts M.2 Type 2280ss SATA drive
• Data Transfer Rate: 6GB per second
• Device Type: Internal Solid State Drive
• Storage Capacity: 500 GB
• Form Factor: 2.28 inches
• Hardware Interface: SATA 6 GB/s

My research turned up a few compatible devices from different manufactures such as:

Samsung 970 EVO SSD 500GB- M.2, Western Digital Blue 3D NAND 500 GB- M.2, Samsung 970 EVO Plus SSD 500 GB- M.2. The price ranges from 64 to 109 USD, however the actual transfer speed is the deal breaker. All of these M.2 SSD drives have a less than 3,500 Megabits per second where as the Crucial has 6 Gigabits per second. The motherboard specification is a max of 32 Gigabits per second, the drive specification is 6 Gigabits per second...

The price for the Crucial MX500 I picked was 65 USD, why pay 109 USD for a slower device?

The drive itself has performed flawlessly, the problem comes with my understanding of the M.2 specification, this can be either PCIe or SATA+PCIe. The confusion lies with the +PCIe, meaning there are two slots/mounting points on the H370 motherboard for the M.2 device. One slot is PCIe and the other is SATA only. After installing the device in the PCIe slot (I wanted it away from the PCIe +16 slot where I have the EVGA video card) and getting an error about the M.2 device on power up I went back to the documentation (which is very terse and read it again, then again, and on the third time one word was missing from the #2 slot: PCIe... Well then the device goes into the #2 slot for SATA! DUH!) Why does the motherboard specification indicate that the #2 slot can be either SATA or PCIe?

Once I had the device in the correct slot I had to figure out what SATA connector on the motherboard would lose it's slot in the BIOS, it turns out it has to be #2 because the #1 is for the CD/DVD drive, #3 thru #6 are for a RAID if you wish to have that many drives and use that option, your boot devices can not be in a RAID 5 array, only RAID 0 or RAID 1 for boot devices.

This is not a mechanical hard drive + SSD device; it is a SSD only device. A hybrid hard drive and SSD would occupy a conventional slot on the motherboard and would NOT take up a SATA connection.