I just had heard that having the OS and running games from the same drive could cause bottlenecks. If I went with the first, I would have the M.2 SSD for boot, and the SATA SSD for games and a 2Tb HDD for mass storage. Or If I went partitioning, then I would allocate whatever the OS needs in one partition and have a second for a game drive. Then again have the HDD for mass storage.