Hi Mark -
There are no "points" in Lasalle. Armies are assembled by picking a core list, and then choosing supporting brigades. You don't get a choice in the unit composition within those brigades... but you do have a lot of choices for what kind of supporting brigades you choose.
There is a scenario generation mechanism that is modified by the character of your army list. Some armies more naturally are prone to attack, others to defend. You can make your choice, but if you choose against your army's "nature," you might get overruled. (A French infantry division tends to be an attacker, for example, but not always.)
The attacker places an objective marker, which the defender can adjust to a certain degree. The objective marker has an effect upon the defending army's morale. If he loses his objective, it triggers morale problems and makes it more likely that he will break.
Of course, he might just break anyway, if the attacker has given him a sound thrashing. A scenario can always be just a toe-to-toe slugging match. It depends upon the players, their armies, the terrain, and how they set up.