Since you didn’t mention any specific brand of transmitter, I keep to some general comments about flaperons. On a powered plane with full length ailerons (strip ailerons), flaperons should be used with caution. Deflecting them downward too much will make the plane unstable. The effect is not as pronounced on a high-wing plane but it is still there. Flaperons do help somewhat more for take-off as it gives greater lift in getting off a rough runway.

A greater benefit is to use the function on a plane that has conventional ailerons (ailerons on the outer part of the wing) and reflex them upwards for landing. This washes-out the wing tip making the wing more stable around the roll axis. It also reduces lift a bit. Both help considerably in landing on a gusty day.

Allan