Set the CPU priority to high, here is how to make a shortcut and always launch BO3 in high priority. Don’t alt-tab from the game, appearantly it can break the priority.
In your steamapps folder, locate the BO3 Beta folder and go inside the “players” folder and edit the ini file. Set the value of “ResolutionMultiplier” to 1 instead of 0.85 to get proper pixel ratio and increase visibility.
Set everything to low, disable shadows and transparency. You can leave a simple form of AA on like FXAA.
This runs the game at a decent 100+ FPS on my amd 290x & 3.8ghz intel cpu.