It's a small patch by recent standards, but important none the less.
FPS Counter Display
Press the / key to open the game command line and then type fps (/fps) and it enter to toggle a FPS counter on or off.
Changing Resolution
Previously I had assumed a one size fits all approach and the game scaled to fit your current resolution, I recognize this may have had pitfalls so now I have added a way to change your resolution via the new Resolutions button on the Options screen (once a character is loaded).
A list of resolutions will be provided, with recommended sizes fitting closer to the preferred 16:9 ratio indicated with a gold crown and not recommended with a red mask.
Changing to one of these resolutions will be almost instant, and it should revert back to your original resolution upon exit. Although from this point forth it is recommended you exit the game via the Menu and the Exit choices presented there and not Alt + F4 as it seems Alt + F4 may not always resize your window back forcing you to ferret around in Windows Settings.
There is a FIX.bat file in the Game folder that will forcibly set your resolution back if all else fails.
If you have been experiencing less than ideal FPS then lowering your screen resolution and/or playing windowed (F11) would be your best options at improving performance.