I didn’t open your link but you know you can use the Virtual Monitor (VorpX V24 Desktop Viewer) to get any resolution you want. So it usually doesn’t matter if your monitor is 3400×1440.
What is your VR headset ?
Your link requires a login, so unfortunately I can’t check it. What window do you mean? If it’s the config app, check the compatibility settings of the .exe properties dialog (right click on the ‘Configure vorpX’ desktop shortcut > Properties > Compatiblity). Make sure to 1. NOT enable any compatiblity mode. 2. Use the default High-DPI settings.