Thinking about getting a RaspberryJAMMA, or have just purchased one and have a newbie question? Walls here are padded, come on in and bounce your question off of them!
The monitor may only support high res via VGA... not sure. Sorry I don't have any experience of 'low res' LCD monitors to be sure. Given the monitor will not look like a CRT in low res mode anyway it shouldn't hurt to try high res mode. Not sur eif that complicates setting it up switching with other boards though.
I hit F4 and hit change to 240p only horizontal and now my CGA works for most things clearly. Some games that used to work now are too short on the horizontal but it looks like there are ways to correct for individual games. I will give it a try.