First off, read this blog post
for a better understanding of the command line parameters as well as how to change them in the Steam interface. Its actually pretty easy.
What's not easy is figuring out how to do this with the DRM free version that doesn't use steam. Well, lucky for you I've got your answers.
-Create a new application
-In the first column select "Utilities"
-In the second column double click "Run Shell Script"
-Leave all settings default and fill out the text panel like this:
-"nohup" prevents the game from quitting if you were to quit the launcher.
-Also notice that I use a tilde (~) at the beginning of the file path, thats just because I have a user applications folder in my home directory (something everyone should do, but thats another story) if you have the game in your system level Applications folder, simply omit the tilde.
-When you're all done, save the app as something descriptive of the settings and place wherever you like.