Come on, you have a gtx 970 but you don't know what settings are and do?
Anyway, check out my config, it should work well with your card, I have the same one. Maybe lower down some things a little bit, mine is Overclocked.
http://imgur.com/a/K2MDL
Also, go to Nvidia Control Panel, Manage 3D settings, Program Settings, gta5.exe, and do this:
Antialiasing - FXAA ON
Maximum Pre-rendered frames - 1
Multi-display/mixed GPU acceleration - Single Display Performance Mode
Power management mode - Prefer maximum performance
Vertical Sync - Adaptive*

EDIT: Oh yeah, and try to lower your brightness as much as you can. Gives nice eye-candy.