Can I use a .settings file for my Ubuntu Touch application? Or isn't that allowed? If yes, where should I store it? I'm developing an app that creates files for usage in my app. Should I use XML for that? What should I use? I'd also like users to exchange those created files with other users that have the same app (via bluetooth or the net). Is that possible yet?
In the near future the SDK will provide a GSettings backend to store your application's settings.
Until then, I'd recommend using the LocalStorage module to store your settings in a database.
You can see an example of how the calculator core app uses LocalStorage.