For older games (especially CGA ones) you can set it to 8 instead.
Modes other than none and normal2x require more processing power, so unless you really want the game to look smoother you can leave this setting as it is. "None" will run the game at 320×240, "normal2x" will run the game at 640×480, and the other modes run at 640×480 using various methods to smooth the pixels of the doubled image.
HOW TO MAKE DOSBOX FULL SCREEN AFTER ALT TAB WINDOWS
Unlike Windows itself, D-Fend cannot pull icons directly from EXEs and DLLs. If you don't want all your games to have that Pac-Man ghost icon, you'll need to get some icons and add them into the Icon Manager. Alternately, click Browse and choose your own destination folder. If you hit Generate Folder name it will create a subfolder with the same name as the Profile Name, and your screenshots will end up there instead.