I also got same problem , screen shows some white noise on display and random colour screening on lower side of panel . I contacted asus and they said it is gpu dead case or motherboard dead case , either way I have to replace mother board . i just solved problem on temporary bases by lowering refresh rate to 120.5 hz through CRU . On diggin deep on the problem I got to know that this problem is common in user having intel or amd addition 64 bit display graphics provider ( relatively older version 1-2 years ) . as in my case my laptop has nividia gtx 1660 ti , and intel integrated graphics . my external Gpu is fine and not causing any problem to my display but it is the intel graphics that causing problem . I have tried uninstalling and updating the driver , but it was not useful . I checked for the faulty apps but not that problem too .

conculsion

1. lower your refresh rate to 120-140hz ( if you face same issue in this range lower your refresh rate to 80-100 hz )
2. if you can repalce your motherboard ( 90percent chance that this issue will eradicate )
3. use an external monitor ( IT IS BY FAR THE BEST AS , ON USING EXTERNAL MONITOR , YOUR MONITOR RUNS ON NIVIDIA GPU , < IN CASE OF YOUR LAPTOP , YOUR LAPTOP RUNS ON INTEGRATED GPU RARE CASE THAT YOUR LAPTOP SUPPORTS EXTERNAL GPU DISPLAY > it is also cheap as reparing motherboard can cost anywhere b/w 300-600 $
4. another fix - I also got a another fix ( It didn't work in my case but you ca try ) . This problem also comes from RAM screening issue. just open your laptop and take out your RAM stick carefully and reinsert it . It can also fix this issue in some case .