I used my NVME samsung drive as a game drive for my sandbox games, like skyrim modded and GTA V.
I have directly compared them to being installed on my 500gb sata 850 EVO, and NVME wins every time in game loading. In game, when you are traveling quite fast in GTA V, texture pop-in is somewhat smoother, but overall game play remains nearly unchanged.
Id say save the NVME decision for when you are doing many MANY tasks that require fast loading.
For the most part, faster/lower latency system memory will have a stronger impact than drive speed. As long as the drive is capable of finding the data it needs in a timely fashion, the difference between sata and M.s NVME will be a minor amount
That certainly should not stop you from installing an M.2 drive if you have a spot for it on your motherboard
Even if you simply wanted to test the waters and get a cheap 32gb NVME drive for 40 bucks or something, that would still be good enough to move your paging file to it, user profiles, caching files for internet browsers, etc..
When I went to my NVME for my skyrim modding stuff, nearly everything sped up, as my modding basically creates a virtual drive system (mod organizer) to keep the game folder clean. NVME speeds helped this dramatically.
I personally am using PCIE 2.0 4x with my drive.
