A:Answer What you are asking is what the G-Sensor is for. When it detects a jolt of sufficient level, the camera will save the current video file in a 'locked' folder so the loop recording can't overwrite the video which detected the impact.
if the vehicle were in park mode, the G-Sensor would cause the unit to power on and record for around 30 seconds. While it obviously cannot catch the impact happening, the hope is it will catch the person as they leave the scene.
I have a 1080p dashcam, definitely clear enough to read a license plate of a vehicle close enough to impact you. read a license plate at 50' would be more of a question than reading one 5' away from the cameras. You'll have no issues unless there is unexpected glare, like the sun rising/setting directly in view of the camera, or vehicle light shining directly into the camera. There are lots of youtube reviews on this and other mirror dashcams, they are worth watching. With tall vehicles, mounting the rear camera up high near the roof allows it to be angled downward more, so less likely to experience any glare issues, thereby seeing details like license plates even better.