I believe the topic is too big and too special for a forum thread. It is not something to answer in few sentences.

Still...

In Russian power personal relations mean more than in the "West" and the law means less. Still the law is not completely negligible. Putin and Medvedev are good friends and Putin is the leader - it is more important than "president and prime minister" stuff.

Duma and other democratic mechanisms do work (particularly I believe that Duma is actually responsible for that discussed "anti gay propaganda law" rather than Putin), but not exactly in the way the democratic technology TM prescribes. Namely they don't provide the effective rotation of personalities in power.

There is a balance between federal center and local powers but it is strongly displaced towards the center and again based not only on the law but on many other factors that make analysis really difficult.