Attack range of ranged units

noob question

When using ranged units, I want to make the most of their range (so that for example bombardier cannons fire from their max range, possibly out of range of the opponents ranged units)

1) Must I simply macro them in order to achieve this or is there some stance that will make them do it automatically?

2) If I have a ranged unit on aggressive stance, and order them to go to a certain spot, will they go there before attacking of while they stop immediately when they are in range of an enemy and start firing, even if they haven't reached their designated spot?