Normally, people attribute the things such as the Holocaust solely to Hitler. However, I have also heard that Hitler was more of a figurehead and charismatic speaker for the Nazi party. How involved was Hitler with the actions of the Reich? Was he the policy setter or just its messenger?
Hitler was definitely personally responsible for many of the crimes the Nazi German state committed.
Despite the fact that there was at one point an academic discussion of how weak or strong dictator he actually was, nobody doubts that he was at the center of the Third Reich and not "just" a mere messenger. His importance as the decider of policy is not just evident in direct orders he had given for crimes of the Reich such as the T4 euthanasia murders order of 1939 or the Kommissarbefehl in March 1941 in connection to the attack on the Soviet Union but also in his role as the ultimate arbiter of policy disputes between the various agencies and actors in terms of policy.
This is exemplified by what historian Ian Kershaw terms "working towards the Führer". Accepting the structure of the Nazi state as polycratic with several agencies and actors being charged with was exactly the same responsibilities, one of the priorities in policy setting was the stated or assumed wishes of Hitler. He managed to build himself in the center of the political system, his wishes becoming the most deciding factor in what was to become policy of subordinated agencies.
It was also him who arbitrated disputes and who had the last word on when to go ahead with what policy. For this reason, it is also the opinion of the majority of academia that despite no written order issued, it was Hitler who decided to go ahead with murder as a policy towards the European Jews in 1941.
Summing up, Hitler was directly responsible for many of the crimes of the Nazi state and despite the exact nature of his leadership being something that is still discussed in academia, he was certainly more than just a mouthpiece.
Sources:
Ian Kershaw: Working Towards the Führer: Reflections on the Nature of the Hitler Dictatorship" pages 103–118 from Contemporary European History, Volume 2, Issue #2, 1993; reprinted on pages 231–252 from The Third Reich edited by Christian Leitz, London: Blackwell, 1999.
Ian Kershaw: The Nazi Dictatorship. Problems and Perspectives of Interpretation, (London, 1985, 4th ed., 2000).
Ian Kershaw: The 'Hitler Myth'. Image and Reality in the Third Reich (Oxford, 1987, rev. 2001).
Evans' Third Reich Trilogy.
Christopher Browning: The Path to Genocide : Essays on launching the Final Solution, Cambridge : Cambridge University Press, 1998, 1992.