Glitched green screen when booting into Windows


I have an ASUS X550L laptop which has OpenSuse Leap 42.1 and Windows 7 (1st partition is Windows boot, 2nd partition is Windows, 3rd is an extended partition with Linux and swap, 4th is a NTFS partition to share files between systems - boot flag is on Linux partition). Boot loader is GRUB 2, as default. Graphics card is Nvidia GeForce 820M. OpenSuse with KDE as default.

After I install and boot into OpenSuse, if I boot into Windows a green glitched screen appears for some seconds before the boot continues. At some point, after several uses the Windows doesn’t boot, it simply stops there with the green screen.
I searched for what could be the problem, and I discovered this could be solved if I install Nvidia proprietary drivers in OpenSuse. I installed Nvidia drivers the easy way (aka, adding the Nvidia repos and allowing zypper to install the recommended packages).
Booting into Windows is then fine, however booting into OpenSuse is not. It gives me Plasma and kdeinit crashes and I can’t do anything.
Some more googling… turns out I can’t use Nvidia proprietary drivers if the graphics card uses Optimus - which it does. I re-installed OpenSuse and this time I installed Bumblebee (as it was recommended). The green screen appears again at Windows boot, but for the time being I can still login into it.

How do I solve this conundrum? If I use non-proprietary drivers, I risk not being able to boot into Windows, if I use proprietary drivers I can’t work with Linux. Why does this even happen?

Thank you in advance