Let's get down to brass tacks here. The inner workings of an arcade monitor and old TVs are very, very similar. The biggest difference being that the input signal. Arcade monitors use R,G,B, H sync, V sync (sometimes combined with H sync) and Ground... all separated, and a composite signal takes all of those and jams/jellies them together into one input. The TV is then configured to handle that signal, separates (most often) the single input into RGB and sends the RGB to the neckboard. It seems like there has to be a way to force the TV to either downgrade the signal between the composite input and the neckboard... but I do not suspect there is a way to feed it a downgraded signal through the composite input and expect the TV to miraculously show the image in the desired resolution. .... If the TV is equipped with i480 component (RGB) inputs then there should be little difference if connected to an old PCB or computer.
I still have a lot to learn, am I off point here?