The Comics Retcon Universe is, unsurprisingly, a Retcon Universe. That means all the stuff you've read over the months/years/decades doesn't mean squat. The term "retcon" is a contraction of "RETroactive CONtinuity" for the curious. The most powerful hero and the most like Comic Canon is the Green Lantern, Jade. She is a deus ex machina for tech equipment, instant costume change rings, etc. But only if you ask her nicely.
Everyone else is up for grabs from whatever universe you can pull them from DC, Marvel, Vertigo, Wildstorm, Dark Horse, etc. As long as there is a comic written about them they are fair game.
If you plan to use a Mega-uber-super-powered person (i.e. Superman, Darkseid, Captain Mar-Vell, et al) then contact Lilith (via BCTS) before wanting to be a part of this universe. We're stunting their growth and powers since this Universe takes place in the Real World. That means Gotham City and Metropolis do not exist.
- The Metagene (or X-Gene or X-Factor): Only (approx.) 6500 people, of all ages, in the world have it strong enough to actually make you "Super". This means the odds of someone your character knows having it are not good at all, but possible. In other words, don't go crazy turning all of your character's friends into the new Justice League or Avengers.
- Magic: Exists, but is only being unveiled at this point, at the Fifth Age of Magic.
- Super Ray Guns That Fit In Your Pocket: Only exist in outer space on other planets that are not Earth. And since there is a big war going on out there, at the moment, they aren't going to be coming here any time soon. That goes for a lot of Comic Book Tech. Some cool stuff is just being invented that you might be able to use, contact me if you absolutely need to know for your story.
- Physics: Laws are still in effect, so try to keep it somewhat realistic. If your character weighs a thousand pounds, falling from a building will probably damage the sidewalk, and they'll never be able to find shoes that last for more than a few minutes.
- Existing Characters: Be nice and contact the author's of existing characters for their permission to be used if you want to use them. And return them as you found them unless you get their okay.