If I'm not mistaken, Noble is the 'parity' level, where you get no bonuses and neither do the AI civs. Beyond that, it scales in favor of the AI (build speed, happyfaces, healthcrosses, etc) just like it scales in your favor in the other direction.
As to other cheats like instant or "shared" research betw. AI civs, scads of "how-the-hell-did-they-produce-those" units that show up mysteriously when you invade, buildings that (if you checked with the cheat function in prior games) appear but were never in the build queue... All that seems to be gone. Unless you sign up to give them some bonuses at the diff. level stage, the AI civs have to build and earn everything they get.