Prezi video is a type of virtual camera. Putting the camera behind the presentation is a way to avoid the greenscreen ideas. However, I see it interesting to chain an OBS virtual camera or Xsplit VCam as an interesting camera feeds to Prezi video. For instance, VCam has a nice background removal feature. OBS has a virtual camera plugin as well as easy green screening. With these video feeds your camera image can have backgrounds remove (or applied). This would be a nice feed to Prezi Video.
However, Prezi video ONLY appears to accepts hardware camera sources, not virtual camera sources. In fact, if another virtual camera source is connected to a hardware camera, then Prezi Video refuses to start saying there is a conflict for claiming a hardware camera. Another way to visualize this:
Presenter -> Hardware Cam -> Virtual Camera Software with filtering like background -> Prezi Video with Prezi visuals -> Webcast platform (zoom, meet, clickmeeting, On24, etc) -> Audience