The new Acceptable Radius settings allow you to control at what distance away your AI stops from its move to target. This can be useful for large characters when attacking or using an interaction point.
You can find the settings in the Smart AI component in the Class Defaults, search for Acceptable Radius in this value you can set the distance in CM that your AI will stop from its move to target. You can also set it per move to type such as Melee Radius or Interaction Radius. If you are wondering why there is no Range Radius this is because that is controlled by the weapons or AI attack target instead.