There's practically no benefit of having two SSDs configured the way you explained. The C drive is primarily under load when the OS is booting, file transfers, video editing, virus scans, installing/uninstalling. Once the OS has fully loaded, disk usage comes to almost a complete halt. Start Task Manager the next time you boot your PC and monitor the disk usage. After a short amount of time, it will stop reading/writing data as it has already loaded everything into the RAM and just be in a idle state.
Task manager can be a good teacher to understanding how the computer functions. Everything will start to make sense - for the most part. When you're playing games, you're generally not running intensive tasks like I described. You're playing the game. If you, per say, had 2 monitors and had Youtube playing on the 2nd monitor, that will use some RAM, slight CPU/GPU usage, but nothing major. That's besides the point, though.