If you're experiencing, for instance, your menu elements being too big and going off screen on different screens with different aspect ratios you could use the ViewportBottom and ViewportRight expressions to get the aspect ratio of the screen and then calculate and compensate for the increased size of the elements with set height, set width and some creative math.
At least that's how I did it for my project's main menu. If there's an simpler way to do it I'd like to hear it.