Pretty damn far range if you set it up right. There should be specs in the manuals.
I was a marketing director for a pro av company that designs megabucks classrooms for universities. The designs frequently called for this kind of technology and they worked great in some very large spaces. The ones where the speaker wears a tracking device work especially well. But there are also designs where there is either a carpet with sensors that the speaker can be followed, or I think just some where software helps the camera follow a subject...which is the most challenging depending on the room setup.
I wouldn't feel comfortable offering advice on models, as that wasn't my expertise. We used some Panasonic, but we mainly sold Vaddio, which is a great brand. We were the main AV integrators for University of Cincinnati, but also did work for Xavier, Miami, etc.