To meet the high energy efficiency requirements of solar-powered Unmanned Aerial Vehicles (UAVs), this paper proposes an optimization design framework for a rudder/differential thrust joint control strategy based on incremental nonlinear dynamic inversion, and this collaborative control strategy is further integrated into top-level trajectory optimization. In this framework, the additional aerodynamic forces and moments caused by the asymmetry of the propeller slip-stream are precisely modeled. The results demonstrate that through a rational allocation between rudder control and differential thrust control, the extra flight power caused by horizontal turns can be reduced by 44.5%, and the overall average flight power decreases by 6.2%. In energy-optimal trajectory design, the introduction of differential thrust control contributes to minimizing unfavorable segments in the flight trajectory, resulting in increased solar energy absorption and reduced flight energy consumption. The results indicate that the average net residual power increases by 7.3%. The effectiveness of differential thrust control in enhancing the energy performance of solar-powered UAVs is verified in this research.