Well the game has gotten a lot less complex thankfully i have to add.
Basically its fairly easy and smooth to play (its however, not easy to win).
You got 3 kind of agents at the beginning "Matsuke" (sort of a secret Police who can bribe/counter-spy and remove hostile agents)
The 2nd one are the assassins and Geishas (get those later) (both do the same thing with 1 difference, Geishas are always visible (more expensive) and get "easier" kills, while assassins are hidden and can also sabotage things, open castle gates, stop armies in their tracks (poision supplies)
The 3rd are the Monks - Monks are awesome, every army should have one. Why? Because monks do - Inspire the army = +Moral - monks can also convert hostile agents and incite rebellions. Also now if you have an agent in an army stack it actually does something. In Armies you get WAY better view range - monks inspire and metsuke make you (more or less) immune to agent attacks of all kinds.
Also family and such is much better to manage. You can level up your generals and agents and give them more chance for success.
There is still revolts but they no longer come from squalor. So the revolt mechanic is more in-line with food supply and religion. (Also now you have a global food supply if that is in the positives you get MASSIVE bonus. Its not always the best choice to upgrade castles as they require more food. While more food globally gives you global economic benefits.
There are some mods on twcenter which imo are needed (more moral / no campaignAI spawns of doom / slower walk speed for foot infantry)
Generally the SP game has gotten WAY better. But there is still some complexity to it. Its definitely closer to Shogun roots than any other Total War. Only downside i'd have to add is that the graphics are really ugly. Since until they patch it in you have no AA and no DX10 or DX11 features.