Initial problem:
1. Installed 'nvidia', its libs and utils.
2. Set resolution in the display configuration (x11 is already set via nvidia settings and corrected to be the correct resolution + refresh rates)
3. Reboot and resolutions are incorrect again.
4. Proceed to setup via display settings again.
Are you using the driver in the repositories or did you download the driver from nvidia website?
1. In your 'system services startup' config disable 'Display manager', it causes all this crap. You want to let nvidia-settings handle the X display.
2. Log out after the change is made. After logging back in open nvidia-settings (you should be root when running nvidia-settings) and check your settings again, both your monitors should be displayed in the config window, click on advanced and change the setting to 'twinview'. Choose which monitor should be the main display by setting "position"=absolute, set the resolution and refresh rates for both monitors. Press apply, ignore any warning messages that pop up. Your settings should now look like this:
If you don't want twinview then add another x display with the correct config for a separate x-screen. (I use 'twinview)
3. Save to X configuration file and make sure 'Merge with existing file' is checked:
4. Nvidia settings configuration file (bottom of config list) must be saved aswell, overwrite it.
5. Log out and in again. If you check nvidia should have retained the settings.
6. Last thing to do here is 'system configuration'>>>'Desktop Effects'>>>General tab
7. Enable desktop effects if you want 'eye candy'.
My config looks like the pic below except i went for 'cube' desktop switching.
8. Under the "all effects' tab choose what you like if you want fancy animations or effects.
9. The advanced tab is important, make sure the settings are set to:
Compositing type: OpenGL 3.1 (or 2 but 3.1 is better)
QT Graphics system: Raster (NB. Make sure it's on Raster and not 'Native')
Keep window thumbs: 'Only for shown windows'
Scale method: 'Crisp' is ok but I have better results with 'Accurate'
Suspend desktop effects: enable this with a check.
Opengl Options: NB. 'Re-use screen content'
Enable colour correction: leave unchecked.
I'm not sure if its driver related or because I said start a new session instead of continue previous session. The tearing crops up when I drag a window from my one monitor (144hz, 1920x1080) to the other one (60hz, 1440x900) or its kinda their in smplayer
Set it to 'previous session' or you'll just go round in circles. Smplayer is my video player of choice, make sure the video settings are set to vdpau and hardware rendering is on.
The only other odd thing I noticed is when I change the display setting via display configuration (not via nvidia settings) and then click on overview to go back to system settings that window just closes. This might be plasma5 related or something else.
As i said above, disable Display Manager. If after disabling it and logging back in you get a blank screen you need to reinstall your driver from the terminal. You can do this using zypper or whatever package manager Arch uses to install your correct driver from repositories. Or install manually if you have the run file from nvidia. In both cases you need to be root and have dropped into runtime level 3 (init 3). After install resume run level 5 (init 5). Should get you back to a GUI login screen.
Hope this helps a bit, all going well you should now have dual monitors sorted with 0 tearing or flicker.
Good luck!
One more reason why I love AUR <3
I think I should just stick with Noveau since I only play games/watch HD videos on Win8.