Usually vertical lines or bars/bands are due to issues with the LCD Panel. Horizontal lines & most other display related issues are usually caused by a bad GPU or memory. With a 15" or 17" model, a bad GPU is unfortunately a real possibility, but there usually is no good way to confirm a GPU failure since the symptoms can be so varied for these MBPros.
The white screen could indicate a GPU or other hardware related issue such as a bad hard drive.
You can try connecting an external display to see if you can see any video on the external display. Putting the laptop into Clamshell Mode would be best......Have the Power Adapter, USB Keyboard & Mouse, and external display connected.....power on the laptop & close the clamshell lid to see whether anything appears on the external display or if you still just get a blank screen.
You can try booting the Apple Diagnostics to see if any hardware issues are detected. Unfortunately the diagnostics rarely detect issues, but it never hurts to try. Plus in this case, if you can see the diagnostic screen, then it may provide a clue to the problem....at least it provides more information & clues.
You can also try booting into Internet Recovery Mode using Command + Option + R. I am suggesting Internet Recovery Mode instead of local Recovery Mode just in case there is an issue with the internal boot drive. If you can access recovery mode, then you can try running Disk Utility First Aid on the physical drive, then on any Containers & volumes.
How to repair a Mac disk with Disk Utility - Apple Support
Have you tried an SMC Reset and PRAM Reset? Hold the PRAM Reset for at least three chimes.
Try booting into Safe Mode since it uses a more basic video driver that perhaps could work around possible GPU issues and it also prevents third party software from automatically launching during boot & login.
