How can I set a custom screen resolution for my Android TV box?
I had found a similar situation using a TVbox, a was trying to change the resolution to full HD (1920x1080), the solution was:


Activate the Android as developer mode on TVBOX, via USB to USB cable execute the following command via command prompt: 

adb shell wm size 1920x1080 #To change resolution into FullHD


or

adb shell wm size 1280x720 #To change resolution into HD

Reboot the device (adb reboot)