The wiki page for UserGameSettings seems to be missing a lot of references to the properties that are available for this object, it only shows RotationType in the properties, but it should have way more:
http://wiki.roblox.com/index.php?title=API:Class/UserGameSettings
Here is a (near?) complete list of properties for this object:
http://anaminus.github.io/api/class/UserGameSettings.html
The pages for the other properties do exist, but it seems like they aren’t linked properly on the UserGameSettings page. For example, MasterVolume is a property of this object, and its page links back properly to UserGameSettings, but you cannot get to this page from the UserGameSettings page:
http://wiki.roblox.com/index.php?title=API:Class/UserGameSettings/MasterVolume
Moreover there seems to be some weird text at the bottom of the UserGameSettings article, of which I’m unsure what the purpose is.