That's a pretty big topic, and will likely need some sourcing from your end as well. All I can say for myself is that the common theme through university classes on medieval history was that feudalism was both caused by and a cause of decentralization. Monarchs would have much theoretical power but far less practical power to do what they want. Oftentimes even in situations where grants of land were not intended to be hereditary they became so (mid to late Ottoman history is a good example of this).

I've got the TWS2 rules revisions, work, and a night out with the wife this weekend, but I'll look through the books I do own on the subject when I can.

In the meantime rather than collect a few dubious internet sources or quick, possibly out of contexts quotes from flipping through aforementioned books I posted a thread on the topic in the monastery, where there are people more qualified than I to try to settle the matter one way or the other. The thread can be found here.