If you love to start small as a country/nation/character/whatever in a game and expand lots this game will be great for you. It's not a pure warfare game and you will have both internal and external threats, but as a purely military strategy game it has plenty of depth.
How many games have both internal and external threats that are set in medieval times that feel natural? I can think of one other... but I'll give you a hint it's CK

V (ck2's predecessor) and it's pretty obscure and hard to guess. If you want to focus on powergaming than not only do you need to compare external threats (which political entitiy/country has the most strength... and maybe I should ally with this one etc) but you also have to deal with several other things. I think the best way to put it would be like this.
Fun things to do as a powergamer:
-Choose when to attack or not
-Make sure your defenses are strong enough so that when another realm is able to attack your realm you're able to defend yourself (in ck2 if they don't border you and don't have any claims on your titles medieval law may say that the enemy AI country cannot attack you without pissing off the pope so they won't)
-It is very similar to 4x games... you could make a 4x mod with this game engine fairly easily (it would take 100s of hours to make though obviously)
-Choose who to marry your daughters off to to gain alliances
-Do you want a smart wife or a lusty wife?... this decision may influence how many daughters you have
-As king, keep check on your counts & dukes.... assign them titles in a way that makes them fight each other instead of you
-Raise or lower the authority of the crown to totally change how your kingdom works... high authority doesn't allow infighting for instance. It makes you stronger militarily... but your dukes will hate you for it. How many other games give you options like that?
-Try not to piss of your sons because they might try and kill you early
This game isn't just for roleplayers, if you love to minmax stats there's heaps and heaps of them that you can either ignore or not ignore if you're a powergamer. You can micromanage everything to hell (e.g. look at every single woman when choosing a wife and what her stats and personality traits are and what family she's from) or not... (e.g. choose a random wife... or only look at her stewardship trait and choose the best one... or only choose the youngest wife). The best part is is you can start a new game and each time you can choose whether to roleplay or not, or anything in between. The amount of choices in ck2 are way bigger than "omg I get to be good or evil cos this is fable and the story is even 2% different near the end!"... when really that sortof choice is pointless.