Nice guide but too absolute. This is a complex game, there are exceptions to every rule. For example, I agree that using mercenaries and your own is usually preferable to angering your vassals. But it is also often good to finish a war quickly, particularly when you take advantage of a moment of weakness in a stronger adversary (such as civil war in the Shia Caliphate). Use those vassal levies to take castles by storm, rack up warscore quickly, end the war before your opponent recovers. Vassals seem to mind long wars more than their men being killed in droves.
Where I really disagree, is with your advise on titles. I create as many as I can and hand them out to members of my dynasty whenever I can. Kingdom titles, too. By 1200 my d'Orange family (originally counts) has over 100 living members and holds 6 kingdoms (2 I kept, the others I gave to cadet branches). There is a reason the dynasty view is in the game. Here's why:
Titles held by family members add to dynasty prestige, which influences starting prestige for new heirs and increases your score as well as increases diplomacy. Rulers from the same dynasty are your allies. Most alliances don't last too long, someone dies (your father-in-law, your spouse, etc.), but same dynasty allies will pass on the alliance to their heirs as long as they're also from the same dynasty. Occassional dynastic succession disputes don't weigh up against the help they give in wars against other enemies.
