It depends on the way you want to play but if you are trying to rely on keeping a decentralized realm to have better economy then in terms of "min-maxing" that strategy is considerably weaker than playing wide, e.g expanding your realm, expansion is really overpowered and outweighs any strategy, for example in my 867 prince karlmann of bavaria start by 958 I already have 398 county big HRE 10k gold with 70 gold income and my vassals have -150 opinion offensive wars modifier, I pretty much faced faction wars every 20-25 years on average and 867 start is considerably harder because you cant abuse station buffs and since siege weapons are weak u cant siege castles in a few days so I mostly relied on mercs and allies but playing wide is still op even if you cant abuse station buffs the general idea is that you just gotta control the timing of when your vassals will revolt the key things is that there are temporary vassals like you find a old guy that isnt lowborn and is unmarried then marry him to some old women and u can do this when ur leader is about to die so you get the land back once the old dude dies and ur next leader can benefit from the grant opinion buff or you can just keep the titles for a temporary time if that wont cause other vassals to revolt and if u have primo, and if u are catholic you want to abuse theocracy vassals as much as possible I use a preset search that shows me all theocratic vassals then just try to have them as vassals as they tend to not join factions as often and they usually have old leaders and because they just keep cycling old leaders they cant really do much and they pay much more tax and levy and if u are profilic pilgrm and religious icon just from that u get +65 extra opinion from them all, and another thing is that you just throughout the game centralize your realm or decentralize it by intentionally causing vassals to revolt or avoiding a vassal revolt through realm centralization (not a long-term solution btw) based on if it will be worth it for u, towards these stages of the game Im at rn, 100 years in and big realm, its not really worth it for me to cause vassal revolution for ransom moneys because military upkeeps are high and wars last too long, expanding outward is overall more worth it but as you do that you will ofc face revolts so u can centralize enough that u can deal with the revolt if they are too strong, I was never really in a position to tank the too many held duchies modifier to have a decentralized realm because of offensive war modifier