As far as genetic modifications go, I'm finding one of the advantages of the setting is that outside of major and obvious differences, I don't really need to make comparisons with our time. That is, if everyone is healthier, smarter, etc. than 20c. Humans, then only differences between the breeds and individuals matter.

As far as longevity goes, it's pretty much a self-solving problem, because even if old age won't kill a person, eventually the odds will catch up with them. That said, I'm still giving Old Humanity a reputation for longevity. It's part of their mystique.