각각의 카메라에 Cinemachine Brain 을 붙이고 CullingMask 를 겹치지 않게 셋팅해야 함.
https://forum.unity.com/threads/can-i-use-2-camera-with-cinemachine-brain.483241/#post-3150079
https://forum.unity.com/threads/any-word-on-splitscreen-multiple-cinemachine-brain-support.512108/#post-3350922
