Well spotted !

Yes, functioning sub-streams worked better at reducing cpu load for me than the previous method of using Intel cpu hardware acceleration.

That same info, re substream bitrate, fps, etc, is also visible in the "Status" /"Cameras" button in BI, you can see all cameras settings rather than one at a time via the individual cameras "General" page.

How did adjusting sub-stream settings affect your CPU usage compared to the previous Intel CPU hardware acceleration method?

Using sub-streams means that BI5 can do motion detection on a much smaller image, so it save a lot of cpu. It's that simple