In your Mame hierarchy there should be a "ini" folder. All ini files go in there, with the exception of the Mame.ini which I keep in the root folder.
Think of it like this:
Mame.ini is your raw file. Source material. You can take any component of the Mame.ini and put it in a new file.
For example, my vector games use HLSL but my raster games use GLSL. Therefore I have a Mame.ini, which is set to GLSL, and then a vector.ini (in the ini folder) that tells Mame to switch to HLSL.
With Keep Aspect Ratio, you're telling Mame to either stretch to fill the screen or not. Shooter games I keep at =1, because they look like ---steaming pile of meadow muffin--- when stretched. Therefore, I have a vertical.ini file, which only says Keep Aspect Ratio=1.
Does that make sense?
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