Mario Kart World’s CameraPlay feature can show the faces of two players per console in-game.
CameraPlay uses a compatible Nintendo Switch 2 camera to place live views of players’ faces into the game. Nintendo designed it for local multiplayer and GameChat-related play, adding a visual social feature to races and other activities.
The two-player limit applies to a single console using one camera. It is separate from the number of racers who can participate in a race, the number of players using split-screen, or the total number of faces that can appear across a GameChat room.
Nintendo’s support information also states that up to four consoles in a GameChat room can use CameraPlay at the same time. That creates a larger combined maximum, but it does not change the per-console limit asked here.