Not sure how to phrase this better but Fake Fullscreen seems to ignore the top layer - the character icons, skillbar inventory window etc - if ther is something underneath.
For example if you click on a character icon to select it the currently selected character will run there and only after that will the character you clicked on be selected.
If you open inventory and click on an item (left or right), if there is anything on the ground behind it then the game interacts with that not the inventory item.
Normal fullscreen and windowed work fine for me.
