Their game write-ups, rather, are inadequate and incomplete representations of the characters (some of whom predate these writeups by almost 40 years). Characters in the Realms -- PCs very much included -- tend to have minor, little-used talents and abilities which the published rules don't necessarily model. This touches on your point about spells: the Realms has a vast array of spells (it's far more 'high magic' in variety than in quantity), a larger array of common spells than assumed by D&D, these are available to PCs through roleplaying, and most of the new spells in Ed's novels, at least, have published or unpublished game writeups -- this is a man who at one point didn't introduce new magic into his campaign until he'd had it published in Dragon.
I don't agree with your evaluation of Khelben's information network (and don't recall anyone except you mocking his stats(!)), but given that, it's they who gather the information rather than he. This is another central point about the Realms: what and who you know are more important than the numbers on your character sheet.
Nightfall's question, though, was about dragons and demons, who don't fight in many novels that I recall.