950 Pro M.2 PCIe Gen 3.0 X4 > 2000 MB/s
850 Pro SATA SATA III = 540 MB/s
850 EVO M.2 SATA III = 540 MB/s
I will let you make the decision.
Also the M.2 have different keying so the EVO may not even fit in your socket
The 950 Pro, for sure.
The 850 EVO m.2 supports only SATA signaling and does not support PCIe signaling at all. In addition, it may not work with all motherboards since the m.2 ports on such boards support only PCIe signaling. Thus, even if you can get the 850 EVO m.2 to work on your system it will be restricted by the m.2 to SATA bridge chip to only about 600 MB/second tops - barely any faster than the 2.5" SATA version of that same drive.
I think I'll go with the 950 pro then. After I install it, with my current set-up above, ideally, what should be hard drive set-up look like with what I have, if don't mind recommending. I'm editing with CC 2015.
Thanks for your help!
I personally would use the 950 Pro for the project files and the media. Leave your media cache and files in the default location the 850 Pro and cleanup (delete) regularly. Use the hard drives for backup/archiving.