The new ssd tech is called nvme and can be used in either a m.2 slot, u.2 slot, or the pcie express slot from an add in card. The fastest transfer speeds make use of pcie 3.0 x4 but not all older boards may support this and instead might use either pcie 3.0 x2 or pcie 2.0 or even sata3.
The main luxury to nvme drives is its sequence write and read. One example is if you open a game from desktop it uses sequence read to load the game faster same with loading maps and levels and whatnot. Another big advantage is if you download a lot of mods for games first you download it which is subject to your internet speed but then you install it which makes use of sequence writes.
The most use for day to day is going to be random reads and writes though and while the 950 pro does have a random read of 12,000 iops over the 850 evo 10,000 iops in 4kb qd1 this isn't the real reason to put games on an nvme drive. The new 960 evo/pro increases that random read to 14,000 iops in 4k qd1 which should be a bigger step forward from the 850 evo but the big advantage to nvme drives is its sequence read and writes and also the less heat generated on the 960 series over the 950 series.
If you are in a position to buy the luxury which is an nvme drive as a gaming library you are going to want to wait for the 960 evo/pro 1tb or even the 512gb. I have the 950 pro 512gb and have only used 250gb for my os and five games one of them being heavily modded skyrim. For sata 3 ssd's you want to use less than 3/4's of the drives capacity to retain its speeds and not use 256/256gb which I think works the same on the nvme drives.
Edit: I'm also learning as I go and apologize for any mistakes or misinformation in that but should be a good starting point for you to do your own research on if buying an nvme drive is worth it for you.
Edited by New green - 10/9/16 at 6:11am