Might be some help to some.
Low FPS Fix for Nvidia:
According to a report from Dishonored 2 early players, Arkane Studios failed to optimize the game properly and a result FPS performance is not up to the mark. Thankfully, a small trick has been discovered which drastically improves Dishonored 2 FPS performance on Nvidia cards. Reddit user Snundae reports:
"After using the Nvidia control panel to change the program-specific settings for Dishonored 2, and changing the maximum pre-rendered frames to 1, my FPS is now a constant 60-150FPS"
Many of you might not be aware of the steps to access this "maximum pre-rendered frames" setting. Follow the steps provided below:
Step 1: Go to Nvidia Control Panel
Step 2: Then to Manage 3D Settings
Step 3: Then to Program Settings
Step 4: Select Dishonored 2
Step 5: Select Maximum Pre-rendered Frames
This trick makes the game run smooth even on the roof top parts of Dunwall at a high graphics setting. I used the term "TRICK" to describe this workaround because this was applicable in the Battlefield 1 and Arma 2. This trick reduces CPU load.
Additional setting changes (try these additional changes also along with pre-rendered frames if above thing does not work):
Set Power management mode to prefer maximum power. If you are using Vsync then use Adaptive Vsync and switch off the in-game Vsync. Also, make sure Dishonored 2 is running in the fullscreen mode for this to work. Also, We recommend you to switch off HBAO+ in game setting.