It is possible to sign in using Apple ID if you wish. Games can be connected to both an Apple ID and a Facebook account at the same time. If you have more than one device using your Apple ID, you will be able to play across those devices. We recommend reading the FAQ on playing across devices.
Please note that you should note down your unique numerical Runaway User ID for your game still because we will not be able to locate data using Apple ID.
To stop using an Apple ID with a game:
You will need to go to your device settings, then select your Apple ID profile. Next you should select "passwords and security" followed by "apps using your apple ID, select the game and choose to stop using Apple ID.