default audio output

It’s like that on mine and the default audio should be the HomePods assigned to the same room your Apple TV is using. Are you saying the bedroom HomePods are wrong because it’s not a bedroom Apple TV? Can you not uncheck bedroom HomePods then select the correct ones? Or are the desired HomePods not signed into the primary user? Look in the home app and also ensure they are assigned to the correct room and not in a default room. All devices should be on the same home wifi network as well.

Unless your ATV is connected to ARC you can disregard that setting (it can only be turned on if connected to ARC)

if you aren’t able to select the HomePods that are in the same room you will need to reset AirPlay & Homekit. You can do this by going into Users & Accounts - Default User (Your Name)- sign out of iCloud

Restart ATV. Once restarted, sign back in and set up AirPlay & Homekit again. At some point it might ask you if you want to set up home theatre, so agree to that or make the HomePods the default audio again.

Set up home theater audio with HomePod or HomePod mini and Apple TV 4K - Apple Support

Ok I missed seeing this post. Glad you figured it out