Dishonored 2 has been slammed on PC, almost exclusively because of its reported performance issues. Developer Arkane Studios and publisher Bethesda have responded in two ways -- a post containing "general recommendations" and another regarding a patch planned for "the coming days".
The recommendations come as an addendum to the game's original launch FAQ. They focus on "bang for buck" graphics options, as well as general playing advice.
Here are the important bits from the post:
Avoid using Alt-Tab when playing. Relaunch the game if you see performance dropping after using Alt-tab. Avoid having background applications running in addition to the game....
If you have performance issues, try lowering the resolution. Use 1440p resolution only if you have a very high-end GPU ( GTX 1070/1080 or equivalent) Keep the V-Sync activated, especially if you have large framerate fluctuations. If you have framerate under 30 fps, adjust the “Adaptive Resolution” between minimum (50%) and default value (75%)....
Use the “Auto” presets: this should adjust your visual settings without impacting your framerate. If you still have performance issues with “Auto” presets: Try deactivating the “TXAA Anti-Aliasing” Try lowering the texture details
As for the patch, no date is provided other than "in the coming days". Along with better performance, the update should address mouse-related input issues:
We have been monitoring the PC forums and social channels and while we're excited to hear that many of you are enjoying the game, we are disheartened that some of you are experiencing PC performance issues on some systems.
We are actively working to provide an update to address your concerns. The patch and its release notes will be available in the coming days.
With the feedback our support group as received, we are preparing a patch intended to provide improvements to allow for more consistent framerates on affected systems and provide an update to the mouse code for smoother input.
Dishonored 2 – Launch FAQ [Bethesda]
Dishonored 2 - Coming Updates [Steam]