Force aspect ratio correction will stretch 320x200 games to 320x240 so you get the right aspect ratio, but since 240 isn't divisible by 200 you end up with some of the original pixels being twice the height of the others. It looks a bit uneven. The pixels of 320x200 games were 1.2 times as tall as wide, or 1.2:1. They weren't square. Ideally, these games should be run at 1600x1200. 1600 / 320 = 5 and 1200 / 200 = 6 so each original pixel would be scaled up to be 5 pixels wide and 6 pixels tall. Since 6 / 5 = 1.2, they would then keep their original shape.
In ScummVM, OpenGL can do this because it performs aspect ratio correction and rescaling in one pass. The problem is that the GUI doesn't allow you to specify a resolution directly. You have to resize the window manually and hope it hits on the right resolution.
DOSBox lets you set the resolution directly in its config file.