If you download the game from Steam, then the Steam client will always run, when you play GD. It basically verifies you are licensed and downloads / installs the game and updates. If you have no internet connection, you can play offline. Or you can set Steam to offline manually, even if you are connected.
GD settings are usually managed within the game. Steam offers a lot of stuff, which I have mostly ignored in all these years - things like community, trade, Big Picture.
My Steam properties for GD:
- By default GD saves your characters in the Steam Cloud. Disable it in GD or Steam, if you want to store your save files locally.
- Originally GD was only an x86 (32-bit) application. If you add /x64 to the launch options, your desktop shortcut will start the x64 version.
- If you want to play with a controller, you can either configure it via Steam or GD’s keybindings.