The scale is not set. A unit's default complement is 300 men but that can be edited to be whatever you want as losses are recorded as a percentage. The actual number of men in a unit has therefore no bearing on game play. Only the percentage of the full complement has an impact.
In terms of distance, arrows travel 4 or 5 hexes regardless of how big the hex is supposed to be (technically related to the number of men in a unit). There is a fair amount of abstraction (including time) as it is a top down design.