Yeah, that's what puts me off. I've used ultra-big monitors at work and screen sharing was always a faff having to resize and share specific windows especially if you need to jump between apps. I like being able to just share the screen, and also that I can maximise to just the one screen.
That's why you want two monitors. One for doing most of your work on and you can share and drag random stuff to.
I have a QHD I use for most things and a 1680x1050 (WSXGA+?) at the side which I share and video conference with. My camera sits on the top of that one.
The only issue with using the ultra wide is my colleagues complaining about the size aspect when screen sharing in meetings.