depends on what you mean. there are mods that give various options. we can raise terrain and dig new rivers and dohave mods for placing water. different mods change the grass, trees, plants that grow, and the animals that roam the land. others alter the climates or alter the dirt and rock textures. various mods can b used to dictate the start settings including buildings or # of bannies.
beyond that it is limited. we can not tell the map where to put the river or hills. the raising terrain tool doesn't give sloping hills. they do flatten out as ground is raised. we can't specify where the main river will be. the map code can bring in a huge variety of maps and that too can differ by mods used.
all depends on what you want to design or change.
