You can impact drive with the drill, but its not very impacty since its just the clutch doing it.
The drill in the combo pack is a toy. Mine stripped out the gears the first time the going got hard on it, whereas the seperate hammer one is much more robust and has really done lots for me that should probably have been done with a larger drill.
The brushless drill is horrible, dont go there till they make a normal one rather than their silly e torque thing.