Autocross and racing videos posted here will never have music added unless there was no audio in the source video. If you hear music in the video, it was actually playing while the video was recorded.
Dashcam videos are posted for informational purposes, so people can get an idea of how they perform, or how they function.
Product reviews are unpaid, not for profit. If a company provided the product for me to review, I will plainly say so in both the video and the description.