Joe, I don’t have an i-Pod or -Phone, so any specific advice I would give you would be speculation. Instead, let me encourge you to experiment to find the settings that work best for you. Using the great user controls in DVDFab you can make short test files (using the Title Start/End button) and see how different choices of screen size and bitrate effect the image.
Some general advice based on my own testing: it is difficult to find a single setting that will be optimum for all your playback needs–there are just too many tradeoffs, and the TV, iPod and iPhone screens are too different (4:3, 1.333:1 on the Pod, 3:2, 1.5:1 on the iPhone, 16:9, 1.77:1 on your widescreen TV) and the maximum bitrates supported by the mobile devices aren’t really high enough to look good on a widescreen HDTV in my opinion.
The great new cropping/sizing functions in DVD to Mobile can help you make great video for your mobiles (by concentrating the available bits in active video) that may look OK on your TV, but I don’t think you’ll find it as good as a DVD. But you decide, “good enough” is very subjective.
Maybe some other users of these devices can chime in with their experiences.