The hard cap that keeps you from recording piles of still footage: no movement at all and no person recognised for that long → stop, and treat the current frame as the new empty scene. Default 20 s.
No. The stamp is drawn into a copy of each frame; the detector still sees the raw camera picture, so the ticking digits never count as motion.
Two. Click Remove on the old machine to free a seat.
No — a macOS limitation: Continuity Camera is a single device on the Mac side. Center Stage in Control Center switches to the ultra-wide and auto-frames.
Menu bar → Quit Owl Cam, then drag the app to the Trash. Settings live in ~/Library/Application Support/OwlCam and recordings in the folder you chose; neither is deleted automatically.