So what this does is substreams allows the heavy CPU processing to occur on the substream.
Part of the heavy process is not showing mainstream in multi camera view. It will show substream so it will be not as sharp and many of the substream resolutions are different ratio than the mainstream.
You may have to go in and adjust your motion settings because of this, so take a look at that.
But when you solo a camera, it will switch to mainstream.
For most after a day or two, we get used to the slightly lower resolution of multi-camera view, especially for the savings it provides. By the way, NVRs do the same thing.
Your substream settings look ok. You could bump bitrate to 2048 and that would help the sharpness some in multi-cam view.