Steam lets me name my folders and put my Steam games where I want to... You have to log into steam in your browser, and manage it from there. I'm on Windows 7-64. If you're on Windows 8 or 10, you may have to research further into Steam and Windows 10 interactions and attempts to prevent the user from running the computer the way they want.
In the Wolves of the Pacific section of the forum, look at
Silent Hunter 4 and Windows 10 for a few clues, such as the Properties tab of the executable and setting the scaling to disabled, run the game as administrator, and using a "memory manager" to gain access to more of the computer's memory. There's a couple other threads and tips mentioned in that thread. I can't find the other threads...