I'm bothered with how the overextension penalty is calculated - it doesn't matter if your empire is tiny or spans half of asia, that 10 income province will grind your empire to a halt. Honestly those excessive nerfs by paradox so people don't pull a napoleon or gengis gets annoying sometimes. Same goes for the massive tech nerf for non-europe.
My over extension is regularly at 120-160%. Basically I try to run stability boosts and all other relevant actions in the small period where I get all more cores before charging off again to expand.
I definitely hate how I get the same overextension now as I did when I was just Ceylon, the one province and I would capture 5 thingies.
You can still pull a Napoleon, you just have to deal with the rebels that crop up.
For real though I can go on a larger conquering spree in Vicky2 than I can in EU4 and that just doesn't make sense goddamit!
I think perhaps the desire of Paradox is for you to vassalize and personal union a bunch of stuff, plus alliances, rather than actually controlling a fuck ton of land. Plus you can get good colonial powers. Colonies don't set off over extension, they just have super high maintenance.
I'm conquering my way from Ceylon to Kashimir and even with my super charged Ceylon its quite the feat to avoid massive rebellions. And I'm balanced on a razor's edge with regards to loans that I use to finance construction.