Screen tearing will always happen if the monitor and GPU are not working synched.
For 60Hz, screen tearing is visible and happens really often.
It is not GTX970's or R9 390's fault and also not the monitor's fault, if you see screen tearing, it just happens.
To get rid of the screen tearing, you can try to activate VSync and/or tripple buffering.
Be careful, VSync could cause stuttering and triple buffering will increase your VRAM usage a bit.
You will be fine with GTX970
Note:
The ultimate solution for screen tear and stuttering due to VSync is GSync (nVidia) or FreeSync(AMD), you will need a special monitor too.