sansolo , since you are mentioning cropping, I assume that you don't use the letterbox scale option but instead the crop...?
If yes, then the actual pixel resolution of your window and layout size will play a role on how the game will be cropped. A 1280x720px game with a 1280x720px layout will have white space on the top/bottom of a 16:10 screen that has 1280x800 px resolution. If the layout is much bigger than the window size, then at the top/bottom of the screen it will be visible. The same thing will happen if the screen has a 1920x1200 px resolution. On a window=layout=1280x720 px there will be white space all around the layout if viewed on a screen that has higher resolution.
However, if you use the letterbox scale, then on all of the ratios that you mentioned, there will be black bars on the top/bottom. In fact, if we keep the order of the ratios in your post the bars will be incising in size as we get closer to the 5:4.