A priori you don't need magic for any of the points you mentioned, though you do need some explanation for having a gravity similar to Earth's in a planet that it is twice the size.
A planet with the same average density as Earth and double its radius, as you propose (Earth has a 40000 km circumpherence), will have eight times the Earth's mass, but since the surface will be twice the distance from the center of mass and gravity decreases by the square of the distance, surface gravity in your planet will be twice that of Earth. That's "similar", for some values of "similar", though rather uncomfortable for actual Earth-born humans.
If you want your planet to have less surface gravity then it should be less dense. The problem is that the elements (iron, nickel) needed for a massive core that can generate a magnetic field (which is somewhat of a requisite for surface habitability of complex organisms) are heavy.
The planet can rotate at any rate you want, within reason. In general we have found that larger planets rotate faster, but that's not a hard-and-fast rule.
If you're willing to work with twice Earth's gravity, then you don't need any magic. Even in that gravity normal humans will be able to live, if not very comfortably. Natively evolved beings should have no problem at all.