Are you talking about the description.ext, or an addon's config.cpp?
The commented config's are an example of the latter. For the former, I'd suggest this tut:
description.ext file descriptionThe first half of that is good, but the second half (which covers sounds and campaigns) isn't so good. If you want to learn about defining sounds, check bloodmixer's sound tut. For campaigns.... do a search. I found a good tut here a while back, but can't remember where it was.
Oh, and on the specific question:
1. in CfgIdentities what are the valid options for: glasses = ? Apart from glasses = "none"
There are also addons that will add more glasses into the game. In that case, check the readme for the name to put there. Or depbo the addon, and find the classnames for the glasses. However, there is no way to check if a person actually has such an addon installed, so it may not work how you want.
BIS's commented cpp's are still helpful, actually, because you can find lots of stuff in there, once you get the hang of them. You can find the names and files of all the BIS sounds, for one thing.