The developers are always working on improving GPU utilization. The only user control is under OPTIONS | EDITING - Use Hardware Accelerated Video Effects. Likely doesn't affect export.
Exported a 2:30 project with eight video/audio tracks here at default mp4 720 resolution with the H264 compressor...
Videopad CPU averaged 33%, GPU 28%. with acceleration ON or OFF. Export time was close to three minutes. Version 8.45.
Video editing is resource intensive and a reasonably high-end PC is recommended.