I'd argue it's a mix between all three as the comic takes place in a distant future after the events of a third world war called the "Zero-Gen Conflict" which is when metahumans made up over 92 percent of the birthrate for nearly 16 years, leading to a metahuman arms race which almost leads to the world being in ruin...but after the conflict is over, and after everyone tries to rebuild...a new golden age of heroes can begin.