Depending on how your placing UI and/or game elements, try using either Scale Inner or Scale Outer full screen mode. This can be found on the project properties bar.
You'll also need to extend your background outside of the viewport. For example, if you are using Scale Outer with a 16:9 aspect ratio, you'll get black bars on both sides on devices that run a larger aspect ratio. Stretching your background outside of the layout will solve this.
And to remove navigation bar or status bar, there is an option on export to hide this.