The difference will be little, but Windows 10 tend to use less resources as persay unlike Win 7, so it's more RAM, DISK and CPU conservative in some aspects, but mostly for PUBG the PC specs will be the biggest factor here, in my case with an I5 4690K and a GTX 970 plus Win 10 OS, I still had trouble with the game with some stuttering when driving and even fps drops here and then, I recently upgraded to a GTX 1080, and it did an enormous difference in the game, can run everything on Ultra despite Post Processing that makes the game very blurry for me, and can still keep at 70 to 92 fps most of the time so yeah the game is not very well optimized for now and is really GPU intensive.