I can't answer all your questions, but this issue with my TCL Android TV is frustrating.
I've had it for 4 years, and due to constant Wi-Fi issues, I keep it deactivated, yet still get occasional notifications.
More concerning, I don't trust the microphone is off, as the LED sometimes stays on, and Bluetooth visibility often resets.
The software is great, but I wish the phone itself was more like the Galaxy series—lighter, thinner, and less outdated feeling.