Three of the first four settings are for “number of dukes”, “number of kings”, and “number of emperors”, after all. That is to say, simply generating a random world means you can make it a lot like the base game, only. The biggest difference between a shattered world and a random one is the scope and scale of the duchies and empires that start the game. If you can't use something I suggest here, and you really want it, buy the DLC.
I have almost all of them myself (even bought The Reaper's Due just because it was there when I got back into the game recently), and I'll be writing with that assumption in mind.
Put simply, this game mode richly rewards the completionist above all. Please bear this in mind if you're shattering the world (especially if you're randomizing the religions in the game) since you might just end up with nothing but unplayable factions all over the map. Shattered and Random Worlds will not allow you to circumvent DLC restrictions that lock playable pagans behind the Old Gods DLC, Muslims behind Sword of Islam, and nomads behind Horse Lords, for example. Let's start by making like a god and creating a world.
So instead of trying to cover the whole DLC in one shot, let's focus in on the one mechanic that is absolutely the most literally world-changing one in the whole package: the Shattered World rules.