The "Auto IK" option makes connected bones act as if they are IK. so if you move the end of a foot-bone-chain, the whole foot, but no the model will move. If bones are not connected when they should then you are either using an very old version of the m3addon or you had bad luck with the model and the bones are not connected.
Are there SC2 models with predefined IK keys?
Edit: oh and you can of course also add manually IK bones/constraints yourself. There are a lot of blender tutorials in the web which explain how to do it. e.g.