For anyone who has a dual monitor setup with a UHD and an FHD monitor, I found a bit of freeware that may be useful to you. Having recently acquired a UHD monitor, I quickly learned learned that doing FHD demo screen recordings of the Vegas timeline were of poor quality since they were not using the native monitor resolution. The solution was to manually set my old Dell FHD display as primary and then launch Vegas using the FHD monitor. It works, but is a bit tedious.

The solution--Monitor Profile Switcher, which enables you to save multiple profiles and then easily switch using a dialog that sits on the Taskbar or through the use of hotkeys.

Here's a screengrab of the dialog.

Here's the link. https://sourceforge.net/projects/monitorswitcher/