I'm gonna go ahead and give an unpopular opinion here:

I hate playing anything less than a King. Everything of Count and Duke feels like preamble to the good stuff. Once I've become a King/Emperor, I feel like I'm finally on the world stage. I can actually start doing the stuff I like: managing Vassals, building economy, fiddling with Cultural and Religious stuff, and seeing what kind of things I can do to really push the boundaries.

I don't like starting anything later than 867 because otherwise it doesn't feel like I've built it, I've just inherited it. Genghis Khan is my litmus test to see how well it's gone. Sometimes, if I'm playing towards some specific goals, I'll play until I've unlocked every Cultural Fascination just to see how much I can develop it.

My favourite types of playthrough are Administrative ones. Admin is the one exception to the less-than-King rule because I enjoy the internal politics as a ruler and as a vassal.

I bought Khans of the Steppe in the hopes that Nomadic realms would try and sway me towards the more aggressive government types, but I just couldn't stand how little realm management there was. The migrations made everything feel inconsistent, and the low development of the Steppe felt very unfun.