Here is a simple trick on how to properly configure Batman: Arkham Knight to avoid lags while playing the game. Take note that the game does not offer an external options editor but includes many graphical options hidden away in it's config files.
How to Configure Batman: Arkham Knight to Avoid Lags
MaxFPS=30.000000 can be changed to MaxFPS=60.000000
To disable the Motionblur WITHOUT crashing the game on startup I changed the following
Many hate Depth of Field effects and set that off by doing this
If your still having issues with framerate you can try turning off other options by setting them to False.
For many of the options, it is suggested doing them one at a time and making sure the game runs before you turn off additional ones. However some, like the motion blur ones, may cause issues if you "half" disable them.