There is a setting in the Quality menu called Quantizer characteristics (Flat part priority). The CCE templates provided by vmesquita set it at 25, and the doom9 cce FAQ suggests a setting of 25-30 (higher # being higher quality?). But on some other posts here (I think Incredible) numbers as low as 14-16 have been mentioned.

I usually encode my KDVDs at Q=15, min=64, max=4500. What quality setting should I be using here?

The lower the value, the better are the complex areas but the blurrier are the slowest ones. And of course, the opposite is true also. WIth a value of 100 there are some parts of the screen that don't move anymore even if normally they should move slightly !

Of course, whatever the encoder, the more you try to keep complex scene correct, the bigger is your target file.

The default value is 17. With 25 Vmesquita obtain a file that is smaller without cutting too much on the quality in the hight action scenes.
I personnaly stay on 17 and Inc seems to have the same advice.

Two things:
1) Each time you lower the Quantisizer Caracteristcs by 5 points, you need a QFactor 1 point less than before for the same filesize

2) For stretched resolutions, in my experience, a lower Q factor looks much better because it has much less mosquito noise which becomes much more visible when playing back. By stretched resolutions, I mean 352x480 and 480x480. I generally use 5 when I use 352x480.

One more info: 17 is also the default setting of DVD2SVCD.

the consensus over at doom9.org seems to be that a higher QC of 25-30 is better when encoding at high bitrates, especially for dark or foggy scene. A low QC will lead to blockiness in these scenes.

I guess what I'm more confused about is how QC values affect the encoded video. I think it's fair to say in a generalized statement that a lower Q value will produce high quality encodes but will increase final size. Can something similar be said for QC?

No, you can't.

Q factor affects the quality of the WHOLE encoding. If you modify it, you change the quality of all the movie in the same way (better or worse).

With QC, when you modify it, SOME scenes are better while OTHERS are worse. It's more a matter of "point of equilibrium" to find where Q factor is just a question of finding the best value for a given target size.

okay then, in that case could you explain the benefits of using QC of 17 vs 25, and vice versa? Because I think I'm still a little confused on that point.

All is in my first post, read carrefully the two part starting with "the".

I can't explain better. With different words if you want