Thanks Brian, you're right, I should not have narrowed my question to ultrawide, as any high res display has the same challenges.
In terms of hotkeys, yes Windows key combos are the first to come to mind that get processed by my local machine if my session is in Windowed Mode. The most common are Win+Arrow keys to snap windows to the left/right. Win+R for Run prompt is another one I used to use often.
I'll check out Virtual Display Manager. Is this it?
https://www.ishadow.com/