Power efficiency is crucial in softwarized 5G gNBs due to rising energy costs and CO_2 emissions from the networking infrastructure. SmartNICs have the potential to accelerate packet processing tasks. However, their limited resources and functionalities make handling complex tasks like retransmissions challenging. Offloading operations to server-class processors can improve scalability but also increase power consumption, warranting careful management. This study examines the performance and power consumption of splitting the processing of the 5G gNB between SmartNICs and DPDK-enabled servers. We implement an adaptive CPU power conserving strategy in the DPDK data plane that dynamically adjusts CPU power states using P-states and C-states based on traffic load. Our evaluation shows that when using five SmartNICs, we can achieve 95 MPPS, demonstrating that offloading can boost throughput by up to 40% for gNB header processing. Our adaptive power management limits CPU power consumption growth to a maximum of 11%, compared to 52% without such management, balancing performance and power efficiency effectively.