Question 500gb M.2 for games and 240gb SSD for OS

Oct 29, 2019
On my current system I have a 240gb SSD 2,5" for the OS and 1tb HDD for games and everything else.
Right now im thinking about getting a new SSD just for the games, since playing directly from the HDD makes my PC sound like it's going to fly off.
I was thinking of getting a M.2 format for this, my MOBO (MSI B450 Tomahawk) has 6 SATA III but with a M.2, two of them will be disabled (SATA 5 and SATA6).
So will this setup work? I just have to change the drives I have right now to SATA1 to SATA4 and install the M.2.

Is this OK? I ask this because I usually see people install their OS on the M.2..