Diverse insect wing kinematics strongly influence dynamic stability and flight efficiency. However, few studies have comprehensively investigated the integrated effects of kinematics on these multiple metrics. In this study, we investigated how wing kinematics affect both aerodynamic efficiency and dynamic stability using computational fluid dynamics simulations of a hovering hawkmoth (Manduca sexta). We systematically varied the wingbeat frequency and stroke plane angle (the horizontal inclination of the wingtip trajectory) relative to measured natural kinematics. Other kinematic parameters were adjusted to maintain force equilibrium in hovering flight. We then evaluated the resulting dynamic stability and aerodynamic power consumption. Our results revealed a clear trade-off between dynamic stability and efficiency across variations in both wingbeat frequency and stroke plane angle. The time constant of the most unstable mode, characterised by coupled roll and sideslip motion, becomes longer, and thus more stable, as either the wingbeat frequency or the stroke plane angle increases, owing to enhanced roll damping torque. However, these kinematic changes also generate larger horizontal force fluctuations and greater asymmetry between the upstroke and downstroke, leading to increased aerodynamic power requirements. These findings suggest that the natural hovering kinematics of the hawkmoth are tuned to balance efficiency and stability. This study provides physical insight into the diversification of insect flight kinematics and offers design guidelines for bio-inspired flapping-wing robots.