drivers - How to solve the Ubuntu 18.04 display issues (lagging, flickering)?

How to improve the display on Ubuntu 18.04? I have tried many different approaches presented on this website and none of them have worked.

I have a MSI GS60 Ghost Pro with integrated Intel GPU and NVIDIA GTX 970M, and I'm having the lagging effect when scrolling web pages (on Chrome, Firefox) and very noticeable flickering effect when moving windows.

The hardware and drivers:

alex@alex-ubuntu:~$ lspci | egrep ' VGA|3D'
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 530 (rev 06)
01:00.0 3D controller: NVIDIA Corporation GM204M [GeForce GTX 970M] (rev a1)

NVIDIA GPU:

alex@alex-ubuntu:~$ glxinfo | grep OpenGL
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: GeForce GTX 970M/PCIe/SSE2
OpenGL core profile version string: 4.6.0 NVIDIA 390.77
OpenGL core profile shading language version string: 4.60 NVIDIA
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 4.6.0 NVIDIA 390.77
OpenGL shading language version string: 4.60 NVIDIA
OpenGL context flags: (none)
OpenGL profile mask: (none)
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 NVIDIA 390.77
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions:
alex@alex-ubuntu:~$ lsmod | grep drm_kms_helper
drm_kms_helper        172032  2 i915,nvidia_drm
syscopyarea            16384  1 drm_kms_helper
sysfillrect            16384  1 drm_kms_helper
sysimgblt              16384  1 drm_kms_helper
fb_sys_fops            16384  1 drm_kms_helper
drm                   401408  6 i915,nvidia_drm,drm_kms_helper

Intel GPU:

alex@alex-ubuntu:~$ glxinfo | grep OpenGL
OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) HD Graphics 530 (Skylake GT2)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.0.5
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 3.0 Mesa 18.0.5
OpenGL shading language version string: 1.30
OpenGL context flags: (none)
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 18.0.5
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions:
alex@alex-ubuntu:~$ lsmod | grep drm_kms_helper
drm_kms_helper        172032  2 nouveau,i915
syscopyarea            16384  1 drm_kms_helper
sysfillrect            16384  1 drm_kms_helper
sysimgblt              16384  1 drm_kms_helper
fb_sys_fops            16384  1 drm_kms_helper
drm                   401408  9 nouveau,i915,ttm,drm_kms_helper

I have tested the following approaches: