There is no single “best” answer. A best practice is to choose a Video Mode that best matches the majority of what your camera creates. The easiest way to do that is to use Video Mode = Automatic and ensure you always start with a video from your (main) camera. Otherwise, if you want to set and forget a predictable Video Mode, then open a video from your camera, and look in Properties. Note, the Resolution and Frame rate. Then, choose the closest match in menu Settings > Video Mode.