If you're changing the resolution, you'll need to adjust the Global Values "Resolution X" and "Resolution Y" to match the screen size. If you're using the Room Camera Widget (it's the orange R box, it's not created at the start), you'll also need to change the Window Width/Height values as well. These are primarily for the camera object to properly lock it's position when it reaches the edge of the screen. If you're using your own camera system then you don't need to worry about them too much.
Thanks for the support btw! :D