Alright, some Protips™
- Stewardship is the Big Stat again. It's +1 demesne per 5 along with a hefty tax bonus. Getting a good spouse set to boost only stewardship and you can be rocking around 25 or so pretty easily, which means doubled demesne for most characters along with +40% or so to taxes ontop of it. Its also important because more demesne = more unit bonuses.
- The stewardship lifestyle with demanding payment for hooks and extort subjects is very good for easy money quick. All the stewardship lifestyle trees have pretty good bonuses in fact, but definitely start with those two. Other good early perks to skim through are the -50% casus belli cost in martial and Intrigue's ability to fabricate hooks and fertility bonus. If you are small then the +75% knight effectiveness ability in martial is very good, and the +4 knight capacity is only 2 steps further down the tree.
- You definitely want to breed a lot of family members since that's what gets you the legacy points, so try and set up dukes of your dynasty everywhere you can. Legacy-wise the first 3 blood bonuses are really, really good at letting you incest and breed constant geniuses. The -20% casus belli cost from warefare is very usefull, stack with the martial bonus so you can war and still wrack up the top-level prestige and piety ranks. The first two law bonuses are kind of only good if you are landing a lot of your dynasty members, otherwise they do nothing. Rest of the lines are pretty meh.
- Military wise it seems you want to focus on a single regiment type (aside from also bringing artillery for sieges). It's odd, because the game has a system where certain units counter other units, but the "counter" works less the more of that unit you bring. So if you are 100% Bowmen and you stack all bowmen building bonuses across all your demesne your archers will outmatch all but their "counter" easily and when fighting their "counter" will only get a penalty of like 5-10% because the AI won't specifically mass light cavalry. And the AI will never have a well-managed 10 or more demesne stacking all the same buildings to get uber units. I recommend archers because when archers have +50 atk/def the gap between them and heavy infantry with +50 atk/def is pretty marginal but the cost savings is always going to be there and be massive. Though Light Infantry might also work, they have pursuit stats so they'll annihilate a retreating enemy.
- Easymode succession: Dread. Specifically, capture a bunch of heathens in a holy war before succession then as soon as your heir becomes ruler, execute them. At least for Catholic (and I presume most other religions not specifically tolerant) this causes no opinion/tyranny hit with the realm, but gives +10 dread apiece. So your 1 year old emperor can have 100 dread and the whole realm quaking in their boots at the thought of his little finger pointing at them to be taken to the gallows. Not even joking this was my way out of having my emperor die just days after my first son was born (I had a really well-statted adult daughter too) There's probably a few other easy ways to get dread but this is what I found.
- Some culture groups have "hidden" techs that don't show up for other cultures and can't be gained by converting their region, only by culture swapping to them. From what I've seen most of them are just specific man-at-arms regiments (pretty good ones too, but always exceedingly pricey and therefore not worth it IMO). However there was one very important culture I noticed: Occitan/Basque/Aragonese/Catalan has "Visigothic Codes", which allows early usage of high partition and equal inheritance law from the tribal age. If anyone notices any other cultures with unique perks I'd be interested to hear about them.
- Development you can kind of ignore. Your vassals will develop and thereby keep your culture group's average dev high, and osmosis will cause your capital to sort of tag along. Use your steward for cultural conversion.
- The Chaplain is a bit of a problem. The pope calling crusades plummets your religion's fervor which causes heresies to spawn and your chaplain to become absolute shit at conversion. You really kind of need to create your own religion with yourself at the head to manage fervor. And definitely consider taking the Pentarchy reform if you don't have it.
- Technically, if you really wanted to min-max buildings, the best way to do it is to own a bunch of separate duchies and only hold their capitals alone. This is because there are also duchy-level buff buildings. e.g. if you held 10 duchy capitals and 10 archery grounds you'd have -60% men at arms maintenance and +150% damage/50% toughness. Which would obviously be fucking insane, and that's just level 1, level 3 would be -100% maintenane/+450% damage/+150% toughness. There's no penalty for holding lots of duchies that I can see other than that you'd suffer the normal -25 opinion with counts for desiring your duchy. This would trash your vassal limit pretty hard though.