They've got a lot of the sociopathic stuff pretty accurate (lack of compassion, manipulation, the view of people as objects to be used for enjoyment or gain, very high intellect/IQ) but Hollywood took liberties (as is the norm) with his connection to Clarice as more than an object (a true sociopath simply does not have it in them to feel real connection, they can feel fondness in a way that a person feels fondness for a lamp, or piece of furniture, i.e. useful, but easily replaced) Anthony Hopkins played the part very well, there is no doubt about it.
As far as the serial killers from the 70s, yeah their body counts were unreal, staggering really... I kind of figure it's due to lack of technology as well as the "free and easy" lifestyle that folks had with a lack of connection (Hey guys, I'm gonna hitchhike from here to Cali, I'll send you a post card when I get there safely!) , lots of hitch hikers, open college campuses, nobody to miss people for months at a time due to lack of communication (no cells, email, social media, etc.)