Z87 and Samsung 970 EVO as secondary drive

I have read that in order for NVMe ssds to work as a boot drive on Z87 I would have to manually modify the BIOS but how about using it as a secondary drive for games?

The reason im considering the 970EVO is I have found a good deal on the 500gb version and I do plan on upgrading to Cannon Lake next year.
 


and I thought the ssd would fit into an empty pci-e slot
so I will need an adapter... what's it called? pci-e to m.2? what would write and read speeds be? would it still perform like any other nvme ssds?
its an ASUS z87k mobo


edit: i guess I found the answers to my questions in this old thread:

http://www.tomshardware.co.uk/answers/id-2839021/ssd-pci-adapter-worth.html

so is it correct to assume that I should forget about the 970 EVO since it probably won't perform better than my current 850 EVO because there is only pci-e 2.0 4x available on the mobo
 
It is called M.2 pcie adapter.
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