How often do players grossly under- or over-achieve their ratings? This is my first season in HBD, so my advance scout budget is 14. How much can I trust the ratings to be accurate? I see some players in the minors overplaying their so-called ratings. Is that just a short-term fluke? Will they fade back down to their rating, or might they be better than the scouts thought? And vica-versa - I see a player with a projected overall rating of 81, but when I look at his individual category ratings, they certainly don't add up to 81 in my eyes. And he is not performing as well as a future-81 player should be. So should I trust the stats more than the ratings?

Advance scouting has no bearing on current ratings. 
Current ratings are the results-producers.   
Ignore minor league stats unless you're comparing them to those on your team(and still take them with a grain of salt as some owners care about minors, some don't).