Ended up with a 960 Pro 1tb & Angelbird Wings px1 Heat Sink. For just a little bit more than the M8peY. I'd have gone with the Plextor half height PCIe offering, but the price of that card has too high a premium at the moment in my opinion. Nice card though and like Plextor's offerings.

I have an old post here with my experience with several Plextor nvme drives. I ended up returning them and got one of the pcie models free. It is holding up and a good drive but no other drive compares to a 960 unless you get a good price. The Samsung drives are just killer

A little off-topic ...

The brushed-aluminum enclosure on Angelbird wrk SSDs perfectly matches the brushed-aluminum exterior panels of my Corsair Obsidian tower. And it turns out the drive enclosures can be swapped very easily with the yucky cheap metal enclosures Samsung puts onto it's 850 PRO SSDs, put the best-looking cases onto the best-performing drives! Acetone easily removes all annoying (Angelbird and Corsair) branding without harming, staining, or corroding these brushed-aluminum surfaces.

Sadly, the Angelbird Wings appears to lack this finely brushed-aluminum finish. An otherwise fine piece of tech, though.

I don't think your "HDD" activity LED is malfunctioning. It receives signal/power from the mobo, which receives it from the (M.2) drive ... but the drive just keeps pulsing the mobo with rapid signals because the drive (flash controller chip) is constantly active, it doesn't send any clean on/off signals because it's always doing something. I've seen the LED do this with my old 480GB G.Skill Phoenix Blade PCIe SSD (an OEM-branded Comay CoreRise G24 BladeDrive PCIe SSD) and was able to "fix" it with a G24 firmware revision. Alas, I upgraded to a 1600GB (and now a 3200GB) Comay CoreRise E28 BladeDrive PCIe SSD but none of the available firmwares have "fixed" the LED thing (so I just wired this LED to something else, lol, the flickering bugged me). I've seen Intel 750 PCIe SSDs do the same thing on consumer mobos.