As for the actual differences between the various noise shapings, ATHtypes, etc - I don't know any more than you
But the VBR Quality number, that I understand. Xing (who invented the VBR header that LAME adapted into the LAME tag) had VBR Quality as part of their tag, but the scale wasn't documented as to what's 100% and what's 0% (I guess I could dig out some old Xing encoders and figure it out myself... maybe later ). So in the LAME tag, the quality has been defined as:100 - ((VBR_q * 10) + quality)
So if you encode something as -V4 -q2 the stored quality would be100 - ((4 * 10) + 2)
100 - 42
58
For CBR files, the quality value is useless as it's hardcoded to "58" for everything from 32kbps to 320kbps!
For presets, the quality number doesn't make a whole lot of sense either:58 = insane (320 CBR)
67 = fm/radio/tape (112 CBR)
78 = hifi (160 CBR)
78 = [fast] standard (~192+ VBR)
78 = [fast] extreme (~224+ VBR)
88 = cd (192 CBR)
88 = r3mix (~192 VBR)
99 = studio (256 CBR)
So obviously the quality number is pretty much useless (320kbps is 70% worse than 256kbps?) (extreme is the same quality as 160CBR?)
In summary, disregard whatever this value has stored as any indication of quality - its only use is to derive what -V and -q settings were used for non-preset encodings.