See Main Resolution and Stage Resolution for more information. Resize (which is the default) will attempt to adjust the X Value and Y Value as well as the Height and Width as a percentage relative to the new resolution, attempting to keep all objects confined to their same relative size and location compared to other objects on the screen. Scale will keep objects in their absolute X Value and Y Value as well as their pixel exact Height and Width which can result in Objects being off the screen. The Changing Resolution radio button is where you choose what to do when adjusting resolutions from one format to another. In the Settings Window found at the top of the Main Ribbon, you will see a Video Output section. Clicking that will open a Windows Explorer to allow you to choose a different image for your Quick Cue.
When opening the Quick Cue selector, if you highlight over an existing Quick Cue, the Change Image option will appear.