The volume of your voice on a video is supposed to be very clear for people to hear it clearly and it must not be distorted. It should be a bit louder than background sounds so that it is noticeable. A good control of a microphone can be used to keep such balance. Make sure that the sound is maintained at a stable level during recording so that the audience can have an easy listening.
Yes, your voice must be very clear. I generally keep my voice just a bit above the background music level, around -6dB, so it stays loud enough to be clear without clipping.
My advice is to test the audio on the headphones before uploading it. What sounded quite okay at the speakers may not even be audible on headphones. Moreover, having a steady and balanced voice adds more professionalism and engagement to the video.