I know it has been ages. I just completed my first pre-recorded video interview for a job application. It was interesting! My tips based on my experience:
1) Relax and take a deep breath.
2) Complete the test question to see how you look and how your tone comes across.
3) You will know the amount of time and the question prior to recording. Gather your thoughts prior to starting the recording.
4) Speak at a medium pace, not too fast or too slow. Remember there may be a time delay in how you speak and how it shows on the video.
5) Eliminate background noises and keep it to a minimum.
6) Leave time to smile for at least one to two seconds after each question.
Lastly, know how to sell yourself!