Actually, the custom resolutions are meant to work with either Computer Monitors or with TV's thru a Scan Converter that supports a large scan range (and I'd go with a TView Gold). The scan converter worries about how to display the image on the TV while the PC itself acts as if it were connected to a computer monitor... hope that clarifies...
NVidia cards suck as a rule when it comes to TV out (ATI is much better according to most here), and I don't know of ANY video cards that output custom resolutions using their TV out (including ATI)...
But if you do use the custom resolutions, your game display will be nearly identical to the complicated ArcadeOS / AdvanceMAME setup while still being able to use Windows without too much additional effort...