As I said, it's the same with Columbine (I know I keep referencing Columbine...but it seems like there's a lot of overlap there). Sue Klebold acts like her son was just some poor depressed lost kid who was brainwashed into Columbine by Eric, who she literally compares to Hitler in her book. When the fact is Dylan wrote about going on a killing spree before Eric ever did, and was mocking the victims as they died. Meanwhile Eric Harris' family has never spoken publicly about the spree.
Leader vs. follower dynamics in a killer duo don't really have to do with culpability or which one was morally worse. In fact oftentimes the follower does the "dirty work." It has to do with more who the dominant person is and who comes up with the plan and all that. I think Kam was the more dominant person historically in their friendship, and it's most likely that he was the dominant person during the spree for the reasons I listed.
However I don't think the leader/follower dynamic is as clear-cut as, for example, the DC sniper case. These guys were the same age, same gender, probably about the same intelligence level (or lack thereof -- sorry, couldn't resist), and were friends for 14 years, so they had more of an equal balance of power than many other killer duos. But I do think Kam was still the more dominant one and that it was likely his idea to begin with given he had been to the area many times.