It be nice if games kept their files all under their own folder like the old days. Playing around with the Star Citizen install on the new drive, and it loads a lot faster, but the game still puts its shader folder in the AppData folder structure that is by default on the Windows installation drive with the Users folder. So any aspects the game needs that are on the new drive will get the new drive speed but whenever it needs to hit that AppData content it'll be using the slower drive.
I guess short of cloning the current C drive onto the new drive, I could move the AppData folder. There's a few steps to that though as I understand. It'd likely be nice to have the OS running off the new drive too though I suppose... sigh...