Surprisingly, I have begun running a Champions campaign in my Earth 641 setting.
It's a superheroic campaign where DC & Marvel Universes have merged, and I'm busy coming up with rationale, pruning, and GM's fiat that justifies why the power levels are low, and why the multiple threats to Earth, The Universe, and Everything haven't emerged and haven't driven the populace insane.
I'll post in the future about how I've been trying to translate all this "Session Zero" stuff for super-heroic campaigns into my own setting and universe -- and how I'm actually taking some of the adventures from other RPGs (super-heroic and non-superheroic) and translating them into my campaign's adventures.
I did a lot of writing and thinking about the campaign, because I really wanted to get the types of adventures and the type of campaign clear in my head, before I started. But I also had to avoid the trap of over-prepping for the campaign, because I wanted to leave space for the characters my players build to carve out their own stories and backstories in the universe.
Am also relearning building characters in HERO, and have been negotiating with my players which of our preferred versions of the rules to use, and it's mostly 5th Edition HERO with some carry-over rules from 4th. So, we shall see!