Dragoner already pointed out that there are different types of feudalism and I'll remind everyone that Mr. Miller has stated in the past that he considers the Imperium to be a feudal technocracy.
Of course the real trouble is that government labels limited to a single word or phrase are so imprecise. Just mull over how many different kinds of governments can "fit" inside the label of "republic".
I'm afraid that I must disagree with the above statements.There are not different kinds of feudalism and I don't feel 'republic' is a type of government in itself.
Feudalism is simply a kind of government where the instrument of power is the ownership/control of land. That's all it is. It simply tells the reader what the instrument of power, that allows the top person to be the top person, is.
Democracy tells us that the instrument of power is the ownership/control of votes; plutocracy is the ownership/control of wealth, kritocracy is the ownership/control of the legal system (judges), theocracy is the ownership/control of religious dogma, a junta is the ownership/control of the military forces, etc. etc.
A republic is a state where the state affairs are 'public matters' as opposed to 'private matters' of concern to a monarch. Where state affairs are a 'private matter', the leadership is a monarchy. Thus a republic is simply a non-monarchy.
The main feature of monarchies is that political power is transferred via heirs and bloodlines as opposed to a individual citizen's wielding of the government's instruments of power.
The Imperium is NOT feudal, nor is it a technocracy. Political power does not come from the ownership of land and the leaders are not technical experts governing based on scientific method.
The Imperium IS a monarchy and the instrument of power that allows the Imperium to control worlds is the monopoly on interstellar trade and commerce.
I suspect that the original authors used the term Feudal Technocracy to evoke mental images associated with feudalism, such as oath-taking, fealty and the relationships among nobles that many people feel exist. The technocracy part would evoke images of control through technology as opposed to the actual definition of a technocracy.
I am beginning to feel that the Imperium does control technology, or at least technology production and distribution to member worlds. It controls production by imperial nobles' control /influence in the operations of the megacorps and it controls distribution through trade regulations. The Imperium jealously guards its monopoly on trade regulation and is willing, not only to fight wars against member worlds, but has partially sterilized the surfaces of planets as punishment to those who challenge its monopoly. This might very well be an indication that the Third Imperium is actually a hydraulic empire, but controlling trade/commerce instead of controlling water.
I think my original idea's outward appearances remains unchanged in that the Imperial Army is little more than security services for noble's estate and for the many SPA starports in existence. Other than that, the only real role for an army is to occupy territory, so how would that affect troop strengths and deployment considering that member world's territories are already 'occupied' by the member world's armed forces?