about your culture groups, I have some suggestions, based on idealogies:
there was a nuclear war between two poltical powers - these two powers became the Genetics and Cybernetics, who remain at war. The landscape should reflect a nuclear winter.
Genetics - believe in human supremacy, and try to create perfect humans for this goal. They should have high war-weariness, owing to an intolerance for loss of humans.
Cybernetics - humans who put their faith in machines. Low war-weariness since all their combat units are artificial, so no loss of life.
Mutants - survivors of nuclear war. PTW will allow ruined cities, which should feature in theri landscapes. N.B. Not all of their units need be humanoid. They blame all other factions for their suffering - the genetics & cybernetics for starting it, the ecologists for running away and doing nothing to prevent the war, the Freedom Republic for raiding the mutants for food.
Freedom Republic - rebels against the stale, cold societies of genetics and cybernetics. Believers in personal freedom & the ideals of the pre-war age. Low tech base, but plenty of stealth units.
Ecologists - after the nuclear war, these people retired from interaction with other factions and became isolationists. Now they have re-emerged to reclaim and heal the scarred ecology.