Let's tackle the resolution first....
When you open the ripped dvd folder with DVD to Mobile and edit the video settings, you can see what original resolution the DVD was authored at. Choose a resolution that is closest to that in width and with a height allowing for your preferences of cropping, etc. There is absolutely no gain by going for a higher resolution. As you are in NTSC land, the width should be around 704 but I have seen different sizes.
Now, on to the bitrate which is an entirely another kettle of fish and a very subjective topic and I will try to be very general.
Firstly, the lower bitrates are achievable because the XVid & H264 encoding is more efficient than the original MPEG encoding of the original DVD's.
That said, the bitrate that you require for different titles can vary. A title with fast action scenes will require a higher bitrate than a low action one.
The actual bitrate that you use and will be happy with depends on a lot of variables, such as size of your target display device, distance that you are seated from it, and the actual device that you use to play the encoded files. It also depends on how good your eyesight is and your own expectations.
I have based my own opinions on the following equipment:-
Samsung 52" LA52A850 High Definition TV
Seated 5 metres (~16 feet) from the screen
Files played on a variety of hard disk and network media players connected by HDMI to TV and by optical cable to my surround sound system.
The best way to establish what you are happy with is to set yourself up a test and encode a title at different bitrates and play them comparing to the original until you find a bitrate that is acceptable to you.
I generally compare them to the original VOB's that I have ripped played on the same player.
Hope this helps
Sorry, but there is no magical "One size fits all"
