Cinemachine – Keep all objects in camera view boundary, mixing 2 cameras

Works!
https://docs.unity3d.com/Packages/com.unity.cinemachine@2.3/manual/CinemachineTargetGroup.html

Applies different weights based on tracking objects location:
https://docs.unity3d.com/Packages/com.unity.cinemachine@2.2/manual/CinemachineMixingCamera.html