So based on everyones testing so far and my own research, the helix 2 does not support nvme devices for booting, only sata which means the nvme evo devices won't work. However it appears retail pro devices do work. If anyone who is using a pro device can test this, could you see if the pro is loading it's own firmware on boot? This would explain it working. A classic example of this is raid controllers and some network cards, how during the boot process they'll load their own firmware to allow the device to function on computers who's bios don't support booting from raid/network.
If this is the case, I kinda wish I bought a pro instead of the evo I tried lol.
Anyway, starting a list of known compatable devices for helix 2.
SSD;
Any m.2 sata card
samsung 950 pro nvme retail card [must be retail version of pro]
wwan cards.
Helix 2 ships with a range of cards, for those who are unlucky like me and got a sierra em7345 card which is a buggy extremely unreliable card that only worked 40% of the time. Lucky unlike past lenovo products, the helix 2 isn't locked down to a specific card. I installed the sierra em7455 card and haven't had a problem since, had to make a gps antenna though. Please note, after installing any card, even if windows recognizes it from the start, it won't work till you install official driver package and/or your carriers firmware. till then it'll claim there's no sim installed.
known wwan cards to work well;
sierra em7455
Known not working devices
Sierra EM7345 works 40% of the time, and what's pathetic is this is the primary card they ship in the helix 2. in fact avoid any wwan card that's based on intel chipsets, none of them work reliably at this point. qualcom based devices work great.
Samsung nvme evo devices. Helix 2 can't boot nvme devices without a little help, some devices load their own firmware at boot to bypass older bios limitations.