I have a 2nd large (plug and play?) monitor that functions as an extension of my main monitor. It identifies as #2
The optimal resolution seems to be 1920 X 1080, true color, 60 Hz and the monitor setting at the screen itself is "fill.
Sometimes, when I start up, the image fills the monitor screen; sometimes not. Often I have to drag the icons and task bar to Monitor 2 each time the computer updates and restarts.
If I go to CONTROL PANEL > SETTINGS, The dialog option "Extend my Windows desktop onto this
monitor is checked. If I uncheck it, monitor #2 is disabled.
There is also a dialog option checkbox "use this device as my primary monitor" but it is disabled and cannot be checked.
My preferred configuration is a plug and play monitor as my primary monitor where the image fills the screen at 1920 X 1080 resolution (true color, 60 Hz) with the original monitor active or inactive.
I know this configuration is possible because it sometimes sets up if I cold kill the computer and restart but it is not consistently reproducible.
Please try and solve this mystery.