I've completed a play through of the Banner Saga, and at no point did the absolute numbers of my Clansmen or Varls seem to matter. I understand that there are achievements associated with them, but why buy any food and supplies at all?
Thoughts: This may be a consequence of choosing the hardest fight each time I had a choice. I'm gussing that the armies allow you to bypass fights if they are high enough.
If you have enough supplies you prevent your caravan from starving, this will drive morale up. The higher your morale, the more bonuses you have in combat. For example, you can move farther and do more damage per turn. You can also improve morale by resting your caravan.
In regards to bypassing fights, if you have high enough numbers of Clansmen and Varl, you can risk an auto resolve with your army instead of fighting every battle.
