I would stay with plan b layout myself. The device will allow 4k pass thru and split out the audio to send to your 975. I am not sure how much broadcast or streaming 4k video is available to your new display but I would treat it as a 4K source along with any other 4k source if you can stream better than 1080P. If you connect the TV to the 975 arc feature then any signal coming from the TV will be limited to 1080P and anything above that may not play at all. That isn't a major issue unless you can stream better than 1080P. The manual wants the TV connected to the 975 ARC input for the OSD and to ensure a handshake occurs.