Would suggest H264 for both main and sub stream 1. Turn off sub stream 2 if not in use and if available for this camera.
To save on hard drive space change 15 FPS to 10 FPS for both FPS and I frame. Set the same for sub stream 1.
Try a main stream bit rate that is higher than 8K. It may improve detail but will also take more disk space. Some cameras have a customized setting and will list the max rate. Keep in powers of 2 say 16,384.
For sub stream 1, if you are using a larger monitor and desire an image with more detail then set sub stream 1 bit rate to 768 Kb/s.
