I think I got everything. Country's tactics are partially dependent on your ruler's stats. Other factors include behavior in war ( if you make lots of deals, invade lots of cities, make lots of scandals, defend your territory a lot, etc, but they're mostly short term from what i've seen ( aka you need to defend every single turn to be a defender that way ))
Savage : Strength above to 80, Politics or Strategy are below or equal to 50
Warlike : Highest stat is Strength but Strength < 80, or Strengths is above 80 and Politics and Strategy are both above 50
Defender : Highest stat is Defense
Normal : Stats are balanced ( Strength isn't 5~ish points higher than Defense. )
Diplomat : Highest stat is Strategy
Passive : Highest stat is Politics
Btw I love how Junko is 'Normal' based on this system, and how Reimu starts as 'Savage' because of this. She tends to become a Diplomat because she makes lots of deals with other countries and because she usually has the highest political power.