Doing it as a virtual camera is not ideal at all since the video conference software won’t know you’re sharing and won’t highlight you. Initially I thought this would work by creating a special window or stage which you can share that then contains one or more windows + web cam.
Actually Screegle also has a window called “Screegle share” if you prefer to share that using the regular screen sharing (window sharing really). In meet it works great but in zoom or teams you need to slide it out to be fully in your screen (of course you then can put other windows on top). But the virtual camera works well for me: I don’t even need to ask for screen sharing permission anymore.
Not sure about the other apps but zoom definitely allows you to share multiple windows by control-clicking multiple windows when sharing a screen.