Steam user Kaldaien has compiled a comprehensive configuration guide for Arkham Knight. Users have reported improved performance, texture streaming and graphics quality.
Because Batman: Arkham Knight heavily uses Nvidia PhysX, you can get a considerable framerate improvement by disabling SLI in the Nvidia control panel and assigning your second GPU to be dedicated to PhysX. The game does not support SLI anyway, so at least with this tweak you can get a sort of 'semi-SLI' mode going. This should increase the framerate by around 25%, similar to a SLI profile with poor scaling.
If you have completed the game and its various side missions but you would like to skip the incredibly time consuming task of collecting all 243 Riddler trophies, you can get a 99% complete save file here. This file has all non-DLC content completed, with the exception of the collection of the final Riddler trophy at the orphanage, so this save game will allow you to battle the Riddler and view the game's full ending after collecting just a single trophy.