Arryn's AAR was a great help in me getting a feel for the game "balance" as you call it. Most other AAR's are less detailed and more fiction-oriented, which is fun/interesting, but can be less useful as a learning tool.
Other thoughts:
Here's a thread with some Posts that might touch on some of what you're asking about.
Order of Expansion thread
If someone has 20 castles at turn 21, they probably have the cheapest castle type and are building a castle in every province; this is a very specialized strategy I wouldn't recommend unless you know why you're doing it and what the tradeoffs are (and there are some)
Getting 1 or 2 basic SC's by turn 20 isn't so hard, especially if that's your targeted goal. Bane Lords don't take that much research, and neither does construction of a few items to start them off.
You might also find some other worthwhile discussions here is you search on particular aspects of your question, ie: research and site searching strategies, super combatants, "castling".
Re: How Do You Balance Growth?
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