Grievous man or machine?

Neither. He is only HALF machine and is not even part man. He WAS Kaleesh. Grievous started life as a bloodthirsty war monger with an unhealthy obsession with killing sentients. He was an incredible warrior in his time until a Separitist engineered "accident" almost took his life. He was as good as dead, his killing days over, when the wealthy, Muun Banking Clan approached him with a deal. They would save him and give some sort of life and purpose again, even give him a new body, but he would have to work for them. He agreed and left his wife, children, and old life behind to become the evil Cyborg Droid General of the Separatist army that we see today. Dooku, under orders from Darth Sidious, taught Grievous how to wield a lightsaber, and already having a vast knowledge of weapons, Grievous advanced quickly. Although Grievous is not Force-sensitive, he had become so good at wielding a lightsaber that it seemed almost as if he didn't need it. In fact, Grievous got so good that he killed more Jedi than the Jedi cared to count or were willing to admit. It is quite arguable that Grievous was one of the most dangerous non-Force-sensitive the Jedi ever had the displeasure of facing.