For a world I'm building I would like to have a nation that is a puppet of a larger empire. I know that a puppet state is a state that is supposedly independent but is in fact dependent upon an outside power. It is nominally sovereign but effectively controlled by a foreign or otherwise alien power, for reasons such as financial interests.
A puppet state preserves the external paraphernalia of independence like a name, flag, anthem, constitution, law codes and motto but in reality is an organ of another state which created or sponsored the government. Puppet states are not recognized as legitimate under international law.
I've look at example like Vichy France, and Manchukuo and a few others, but i'm still really uncertain the rules of a puppeted nation/state are...
Added Info from suggestion from comments
To add more of a backstory as suggested in the comments, The conquering empire is one with One-party totalitarian military dictatorship under an absolute monarchy, much like Japan in WW2. The conquered nation (before it is puppeted) was a much like The Kingdom Romania a constitutional monarchy.
The Conquering nation wants to simply wanted to conquer this nation to expand its territories and bring the continent they share under their rule. They desired to create a puppet of the conquered nation to hold dominance and influence the people.
Question: Besides what I stated above, are there any other rules that the puppet state/Nation would have to follow, are there any rules I should consider from a world building perspective?
If anything is unclear please let me know I am always looking for ways to improve.