Change the resolution in the video settings. Also make sure to have the game windowed borderless
Change your video settings without crashing the game (borderless windowed)
Make sure your game is closed before doing that.
Go to %localappdata%\Plutonium\storage\t4\players
Open the config file with the notepad to edit it.
plutonium.cfg is for singleplayer/zombies and plutonium_mp.cfg is for multiplayer
Change these 4 dvars to be like below (you can use ctrl+f to search for them)