See resolutions and supported refresh rate of connected screen Is it possible to select a specific resolution and refresh rate on os x el capitan? I attached a screenshot of paying software which gives you the possibility to do this
Yes.

For your main display you would:


Click on the Apple menu
Select System Preferences 
Select Displays
Click on Display
Select Scaled to select your resolution 


Notes: 


If you have more than one display, you can select from additional resolution options by also pressing the Option key at Step 5.
You'll also see the refresh rate option after Step 4.


If I've misunderstood your question please let me know.