RE: multi-prop and more on a 12FG
Multiprop has absolutely nothing to do with multiple engines. That's a control function that allows you to multiplex several positionable channels off a single channel. For multi-engined aircraft, you set up a channel with throttle functions...throttle, throttle2, and throttle 3. Set the endpoints to suit the carbs on each engine. They'll then be controlled via the throttle stick and trim.
For flaperons, you go into the Function section of the LInkage Menu and set Camber to the desired control, say "LS" (Left Slider). Now go into the Model Menu and select the Camber Mix. There, you can turn it on and adjust how much the ailerons will move when you move the Camber control (the left slider). If you want the Camber Mix on at all times, don't assign a switch to turn it on and off, just change it from "INH" to "ON".
The Camber AFR will adjust how much total flap action to get when you move the slider. The Aileron AFR section will adjust how much the ailerons will move as a percentage of camber movement. Actually, for flaperons, you set the Ailerons to 100% and the Camber AFR to 100%. Make sure you have them moving in the direction you want when you move the slider. You can also adjust elevator compensation so that you get little trim change when you move the Camber slider.