Managing 8 heroes on the map.

In my opinion, it's better to start by learning how to play on 160. On 200, everything heavily depends on the specific situation and map layout. For example, on an 8x12 map, there could be 8 heroes by the third day and around 20,000 free resources on day 121. But on some other maps, there might only be 3-4 heroes on the first day. I don't think there's a way to come up with general advice.
But one hero is always the main character, regardless of the difficulty level.