Is it possible to play Civ 6 or BE on a Secondary Monitor?

If you are using Steam then you can use Steam's Big Picture mode. Go to View > Big Picture Mode. Then go to Settings > Resolution > Target Monitor and select the monitor you want to use. It will automatically move and adjust itself to the selected monitor. Now if you launch the game from Steam it will be properly adjusted to the selected monitor. You may need to switch the game's graphics settings to Borderless Window mode in order for it to be full screen. Also, if the text becomes too small then make sure you tick the UI Upscaling box in the game's graphics options.

If you did not purchase the game through Steam you can still launch it using Steam by adding it as a short-cut to your Steam games library. Hope this helps