I notices that when selecting a Video format for ripping a DVD, there is a Video quality slider that has a default value for each selection. Is this default an optimal setting? If I slide to the right, am I getting better quality or just a fatter file?

Jeff

I think it is an optimal. It will give you increased bitrate and therefore better quality and larger filesize

I would call it a "sensible" default setting.
Typically the displays aren't that large, so it usually doesn't make too much sense to tweak the quality settings and double the filesize even though it is hard to tell the difference on the "tiny display".
But in some cases you might want to preserve the better quality, maybe because you want to plug the mobile device into a TV set or something like that...