I remember doing CK2 games as an Irish count forgot which one, and as a converted Imperator save as Britannia. I also remember somewhat long-running CK2 games starting as Francia and as the Rurikids in 867, but I don't think I played those through all the way to completion. I haven't played a full CK3 game yet.

Tags that will let me get achievements on the way and that will let me imagine nice historical narratives are a plus.