How do you connect your arcade monitor to your PC?
Do you use a ArcadeVGA or a TV out?
Anyway, if you cabinet screen is a 15khz one , all vertical resolution above 288 will be blurred.
A 15khz screen like a TV or a Arcade one can not display 480 lines. So if you use that kind of resolution it will be interlaced , and the result is not very nice.
If you have an arcadeVGA , use 640x288 resolution. If you don't have one use 320x240.
But as i don't have lot of layout native in 320x240 , it will be strechted so text will be not perfect. I suggest you make (or adapt) your own layout to the resolution 320x240.
this problem is not linked to Atomic. It will be the same for all Front End if you use 640x480 or above resolution on a 15khz monitor.