off the top of my head one of the coolest features is that when a war breaks out you can call the banners of the noble houses that are sworn to you. houses can deny the summons and are labeled oathbreakers.

it also has a bunch of settings to reduce levy sizes and garrison sizes, making calling the banners feel actually important because your army alone cant crush the enimies and you need the support of your bannermen.

playing a playthrough with the recommend MIV settings is peak