Here's what I'm running to get 4k
Windows = {
Width3d = 3840,
Height3d = 2160,
DisplayNo = 0,
Width = 3840,
DisableMemoryOptimize = false,
FullScreen = true,
Height = 2160,
VirtualFullScreen = false,
DisableDirectX9Ex = false,
ManagedDevice = false,
The above setting with give you 4K but the UI is super small. To fix the UI I did the following:
From the launcher under Environment Settings I select the Screen tab and change the preferred scale to 1.5 under text size. I don't mess with anything else. Save settings and the UI is larger.
Here's what you'd want for 1440p
Windows = {
Width3d = 2560,
Height3d = 1440,
DisplayNo = 0,
Width = 2560,
DisableMemoryOptimize = false,
FullScreen = true,
Height = 1440,
VirtualFullScreen = false,
DisableDirectX9Ex = false,
ManagedDevice = false,
For 1440p you may want to change the preferred scale to 1.2
Hope this helps
EDIT If you're running the game on a 2nd display like me I also have to change DisplayNo = 0 to DisplayNo = 1