My first PC build

Hi,
I hope this is appropriate area to post.

I have a question. First, I am building a X99 Taichi with a E6800, 32GB and eVga 1080 SC.
But for boot I am stuck at what ssd to use.

The support doc doesn't list the Samsung 960 EVO or PRO 1tb (M.2 Ultra) as supported (not listed). But it does support the 512. Anyone using the 1TB model as a boot drive? Concerns? (I guess I can buy one but I would need to RMA if not workable).

IF not the Samsung 960 EVO or Pro, I found an Intel 750 PCIe card with 1.2TB for not much more than a 960 PRO 1TB. Anyone install a 750 on a X99? I would assume  Upper PCIe slot (closest) to the CPU is for the GPU (I am not SLI a card).
SO I could put the 750 in the PCI Slot (middle).

However, this has me thinking as, what if I wanted to add another 1080 later? Then the Intel 750 would need to move down and lose all speed (PCI 2 and 3 @16x and PCI4 @ 0x)

So, maybe to go Intel 750 (non-PCIe card) with U.2 kit (can't find them online...instock anyway). ??

I want 1TB of SSD boot. Ideally, I got this for the U.2 slots (I thought I could raid them but x99 doesn't support that on NVMe). But is it that ASRock doesn't yet list the 1TB 960 NVMe as they didn't test due something or was it just not updated yet?

Summary:
-can I use samsung 960 EVO (or Pro) 1tb NVMe ?
-Is there a 1TB Nvme that is ~2Gb/s that I can?
-Or better off with Intel 750 1.2TB SSD (and better with U.2 kit or slot)?

Thanks for any help. I have everything to build except the SSD.

I also wanted to ask, How can I request a bios update to support Samsung 960 EVO or PRO 1TB NVMe SSDs?