In all but MAME, my games fit my screen (7″ TFT with HDMI)
In MAME, I have about a 1″ border left and right but the top and
bottom fits OK.
I guess that’s the native MAME aspect ratio but is there a way
to strech MAME games to fit?
If they are vertical scrolling games (1943 etc.) Its unlikely that you’ll be able to get a fullscreen (plus it would look wonky to make a vertical game wide screen- the airplanes would end up looking like tanks) but for games that aren’t vertical, mess around with the video settings by pressing m or x right before your ROM loads (if you are on image 2.4 or later) floob shows how to use it in this video:
There may also be an issue with black borders for your whole system and this video shows how to remove them here: