I know the number of open gates that triggers the awakening of the Ancient One reduces as the number of players increase, and the number of roaming monsters in Arkham increases as well, so there is the crowdedness factor that seems more perilous. Also, there are two monsters per gate opening when there are 5+ investigators. Are there other factors? These factors don't seem as significant or maybe as linearly ramped as the balancing factors in Eldritch Horror where clues, gates, surges, and mystery requirements scale with every 2 added investigators.
The 'limits' that change with more players are:
- Maximum number of monsters on the board before they go into outskirts
- Maximum number of monsters in the outskirts before the terror track is moved
- Maximum number of gates that can be open at any time
- Maximum number of monsters that trigger the awakening of the Great Old One once the terror level has reached 10