The TV is already upscaling everything. The image is being displayed in 8K resolution but there is no actual 8K content except for some Youtube videos that the Q900 cannot play in 8K. I don’t believe it supports AV1.
What are these devices of which you speak? Most will be HDR10 or Dolby Vision capable. Most streaming services use Dolby Vision. HDR10, NOT HDR10+, is standard in HDR content and displayed when any device in the chain does not support Dolby Vision. Most of what you view in HDR on that TV will be in 4K HDR10 @24fps.
Updates to the Yamaha will not improve the image sent to the TV. You will simply be upscaling a 4K or less image that the TV is already upscaling now. When devices are connected directly to the TV, you can go into the TV’s Sound settings and adjust audio output delay. But, it may not fix any issues.
The best reason for connection of devices into the Yamaha is that the TV does not support eARC and lossless audio cannot be sent over ARC. So, lossless multichannel tracks from a disc player would only be available with the player connected to the Yamaha and not directly to the TV. Streaming services use lossy Dolby Digital Plus based Atmos that can be sent to the Yamaha over ARC.
If you are only using streaming devices, the Yamaha update will improve nothing. If you game, the update will allow for console connection to the Yamaha with no loss of console capabilities. If you have a disc player with two HDMI outputs, you can connect number one to the TV and number two to the Yamaha for the best audio and video experience. All HDR from the player will be sent in HDR10 unless the player and disc content support HDR10+.
