Using mirror mode, you will see the same content on the Android device and Wacom One. If the Android device is placed in a horizontal orientation, the screen automatically adapts to full display on Wacom One with certain edge area not working due to the screen ratio. If the Android device is placed in vertical orientation, Wacom One will be limited to the same screen size of the Android device.
Under projection mode, Wacom One works as a 2nd display much like a computer. Orientation of the Android device will not influence of what you will see on Wacom One. See “Connecting my Wacom pen display, Android is only using a portion of the pen display area …”.