B350 Fatality second m.2 slot

Iv got my B350 Fatal1ty board and so far im real happy with it, aside from a not very beginner friendly uefi, but i am confused by the second m.2 slot configuration. Iv been seeing several reviewers use nvme SSDs to test that second slot and are getting essentially nvme PCIe 2 x4 level results AND i believe there it even says somewhere in the spec sheet that the slot is capable of 20gb/s which leads to believe is essentially a PCIe 2 x4 slot. Essentially what I want to know is would I be able to plug *any* nvme SSD in that second m.2 slot and have it work? And more importantly can i boot from that drive? Also, as a side question, would I potentially be able to run both SSDs in RAID, assuming i got them both to function properly?
I feel pretty comfortable with my understanding of the Ultra m.2 slot and how it is essentially double wired to the the lower PCIe 3 x"16" slot and will only really register with nvme SSDs and is bootable from that nvme SSD. But if Ive been wrong at any point please feel free to correct me. I just want some clearified information and maybe help someone else with the same question.

I should have probably given more details but yes you are correct, I am using the K4. The reason I asked if an nvme drive would work in the second slot is its stuck in my head that i read somewhere the M2_2 slot was rated at 20Gb/s. I want to know if I could plug in a larger, yet slower NVMe drive into that M2_2 slot. My 960, that is currently in the M2_1, would fully saturate that connection (assuming it is 20Gb/s) and is currently running at 3,000MBps in the M2_2. Btw I am using a Ryzen 1700 @ 3.9ghz and 16gb of corsair at 3000mhz


Edited by Micktalian - 12 Sep 2017 at 11:27pm

Yes you are correct again lol. But now that we're on the topic, Samsung's magician software says "rapid mode is disabled" for my 960 evo in slot m2_1, what does that mean? There is also a VID 1022 warning type thing. I mean im content with the 3000GB/s but why not max it out if possible?