I'm shocked you got even one m.2 to work! I could find zero info on teh MSI Z270 SLI PLUS and m.2 adapters. I finally just ordered 2 to put the question to rest. DOES NOT WORK.
The A pro version is good, that's the only confirmed 8 gpu variant of the z270 sli plus.
I watched a Bits Be Trippin' video and bought everything he listed. I found that the sli plus is NOT an ideal mobo and i should've bought the h110 Btc+ and been done with it.
If you somehow got this to work, PLEASE let me know what you did. There are no m.2 bios settings in the sli plus like there are in the A pro
While i was disappointed, i did NOT expect the m.2 adapters to work on this mobo. Like i said, the lack of specific m.2 settings in bios was a dead giveaway. $20 to test and not even, i requested a refund and amazon is awesome so sending them back tomorrow. A free experiment to put this to rest once and for all.

I am personally waiting to see how the ethereum mining scene shakes down come november when block rewards are cut AND difficulty STOPS increasing. If it looks good still? I'll buy a Asrock h110 and 2 more 1060s. If not? Eh, no big deal