Mixes are a bad idea at this point. The plane needs to be properly trimmed first, which includes a battery of tests to determine if things like CG, incidence, dihedral, differential, etc. are all set up correctly. Using mixes to fix things that are mechanically wrong with the plane is not the way to go.

Dual rates sounds cool. In reality, we all forget to flip the switch at some point, forget where the switch is, etc. (hopefully) until we've been flying for a while. Set the plane up on low rates and fly it. Get comfortable with it, learn it. Then you can say to yourself "hmm, I feel like it should roll a little faster" and at that point you might just want to increase the current rates, and not have dual rates.

Dual (and triple) are really for setting a plane up for 3D and for competition. I've got two competition planes and really only need dual rates on the rudder for big rudder moves. At some point you'll learn some throttle control, and find out that you can increase/decrease the sensitivity of the plane at different speeds, attitudes, and how the prop wash is blowing over the plane.