Ultimately I'm wanting the best quality possible.
Ultimately, with a project that long, the quality you are going to be able to get is only average. Quality in effect depends principally on the bitrate used. But the higher the bitrate = higher quality = but also the less video you can fit on a disc.
Using a single layer DVD, a bitrate of 8000 kbps will alow you around 1 hour of video, or about 70 minutes with mpeg layer 2 audio as you are using (or Dolby). That will be the best quality. You will still get good quality using a bitrate of 6000 kbps, and that will allow you 90 minutes (or 100 minutes with mpeg layer 2 audio). But to fit around 2 hours on a single layer DVD, you have to drop the bitrate to around 4000 kbps. And that at best will give you quality roughly equivalent to good VHS. But nowhere near as good as with a higher bitrate.
VBR and CBR are important also for the amount you can put on a DVD. With VBR, you can put on more since, if there is not much action, the program uses a lower bitrate for those scenes and thus use less space. More action means a higher bitrate, and less space. CBR as its name implies is fixed and in effect you can work out exactly how much will fit on a disc. I can't give you exact figures, however, but VBR might give you at most a handful of minutes extra, but not so much that it would make a great deal of difference in squeezing all your project onto a DVD.
The 100 percent slider in fact is only meant to represent a balance of the final quality and the speed it takes to render at that quality. I personally never touch the default setting which, from memory, is 70 per cent. I have played around with it in the past, and the extra time taken by setting it higher than that is not reflected by any really obvious improvement in quality. But play around with it yourself. It might just give decent results when talking about the low bitrate you are using. Note, however, that depending on your computer, some people in the past have had the program hang when they use 100. If that happens, drop it back a bit to, say, 90.
The other thing which might improve the final quality a little is to do a two pass encode. That is if you use VBR. The program scans your video in the first pass, and works out the optimum bitrates to use for different parts of it. In the second pass, it actually encodes using those bitrates. In other words, the calculations are more precise than doing it all on the fly in one pass, and the end quality again could be marginally better. Note that two pass will double the encoding time overall.
