Well, at some point, EUIV becomes an automatism. Find a target, smash the target, grab land, find another target.
By the time the Age of Absolutism rolls around, the only serious opposition left to a World Conqueror (regardless of who it is) are the few designed-to-be-powerful nations or group of nations: Ming, the HRE, either Russia or the Commonwealth, and the such.
And of those, usually only the HRE, Ming and a superstrong Russia can really remain a real threat after the first victorious war against them. Everybody else gets significantly easier to fight once you’ve beaten them once.
So the only real enemy left if you can defeat those large countries are the clock and rebels. Because if you play too conservatively, sticking to below 100% Overextension all the time, you won’t be able to conquer everything in time. But at over 100% Overextension, rebels are inevitable.
In my run, I fail to realize that until very late. So the last fifty years or so I need to accept stupid amounts of rebellions (even having to micromanage my armies just to kill separatists rebels before they break my empire in parts.) because I’m stuck going over 200% overextension (and of course, in the last few years I’m doomed to living at Stability -3, because respecting truces would prevent me from finishing in time.)
So yeah… the last few decades are an uneventful slog of moving armies around, stomping inferior opponents over and over and over again. Really more of a chore than anything else. And then I get the achievement and it’s over.
Really, nothing exciting at all.
Biggest lesson learned? It’s not interesting LP material. But it’s over, so whatever.