With the rapid growth of the electric vehicle (EV) market, one-pedal driving (OPD) has become a widely adopted feature in modern EVs. This study addresses two key questions of OPD: (1) Its influence on EV car-following behavior and (2) its interaction with adaptive cruise control (ACC). To explore these questions, field experiments were conducted to empirically compare one-pedal and two-pedal driving (TPD) under both manual control and ACC settings. Statistical and comparative analyses reveal significant behavioral differences across control settings. Under manual control, OPD produces more pronounced speed oscillations and sharper decelerations with quicker responses, primarily because acceleration and braking are managed solely through the accelerator pedal. Drivers, especially those less experienced, struggle with fine speed modulation, resulting in greater variability. These findings highlight the need to account for driver familiarity and heterogeneity when modeling OPD behavior. Under ACC, OPD yields narrower distributions of speed, acceleration, and spacing, indicating smoother and more conservative control, while both modes exhibit similar response delays. This suggests that integrating OPD with ACC can attenuate disturbance propagation and enhance platoon stability. The findings contribute to a deeper understanding of the influence of OPD on car-following behavior and provide practical insights for developing and tuning ACC systems that effectively leverage regenerative braking to improve traffic flow efficiency and system stability.