The QR code is just a faster/easier method of signing in. It doesn’t make a difference for your account info in the app.
If you sign out when leaving, then no account info remains on that TV. You’re all good if you remember to do that.
Go to the in-app Settings, then Accounts, and sign in there. Sign out at the very same spot.
Sign in to the Apple TV app - Apple TV app user guide - Apple Support

If you forget to sign out, then you can remove that device from your signed-in devices list, but then the associated email address will still be visible. Any action on that device that requires account authorization (including viewing subscription content) will then prompt for a password (which a different user wouldn’t have) to sign in again. Check your Apple Account device list to find where you’re signed in - Apple Support
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Else use AirPlay to stream from (through) one of your Apple devices (e.g. iPhone), if that TV supports AirPlay and if you get to connect to the same home network. Then no signing-in is needed at all.
Use AirPlay to stream video or mirror the screen of your iPhone or iPad - Apple Support