What is your model Apple TV? Identify your Apple TV model - Apple Support
Your Apple TV box settings can only be changed locally, by directly interacting with it. Other old devices, no longer in your possession, play no role in this (except maybe One Home Screen, if (still) registered with your account).
What settings appear to be changed? Changed how? We need more clues to try to figure this out.
If you think someone else is using your account unauthorized, then change the Apple ID password. That will then require signing in again on all your devices, which will fail for unauthorized users that do not know the new password.
If you sell or give away your old devices, then you should first reset those to factory settings, which erases all account information and other customization.
You can see a list of devices where your account is being used: Check your Apple ID device list to see where you're signed in - Apple Support