Personally I prefer the reset button if it is easily accessible, but in theory doing the reset in the GUI should be the same.
BI will use substreams for things that can be used for substreams as it relates to motion detection, multi camera views, alert images, etc.
If it uses mainstream for all of that, you get triple or more CPU usage depending on camera resolution and number of cameras.
And more cameras equals more problems.
If substreams resulted in inferior performance, none of us would use it.
Keep in mind NVRs have used the substreams for years and BI was actually late to the game in implementing that feature.
There is no downside to substreams.
You can tell BI to record 24/7 mainstream or to save storage tell it to record continuous + triggers, which will record substream until triggered then go to mainstream during an event and then back to substream, but using substreams allows the computer to do so much more.
Post the BI camera status screenshot showing the total MP/s. It would look something like this example I found with a search (too lazy to screenshot mine LOL):