Ambush camps are better taken out in stealth. The crossbow and melee takedowns are your best option for this. Rocks can be used to lead enemies to areas where they can be taken down without anyone seeing.

Clearing out ambush camps should be one of your first priorities as they clear fog around areas, mark collectibles around the map, and unlock crafting recipes for crossbow bolts which are used to unlock the "Variety is the Spice of Life" achievement.