the second controller will take over if the first one drops its network connection
It can be configured on NetApp but it is not default.
does it default to load balance requests between controller's
There is no load balancing between controllers. Each controller is completely separate, it has own set of disks and exports own resources (shares, LUNs, etc). Client always connects to specific controller. This does not change during takeover - in this case surviving partner starts virtual instance of second controller, so for clients personality does not change.
Any load balancing has to be done manually by administrator - i.e. distributing resources and clients between controllers.