This has a few issues, I think. For example, using bestvideo prevents you from downloading formats that contain both video and audio, it only downloads video-only formats.
> otherwise download the best available
This will potentially download much higher than 720, if 720 is not available. Probably better to go lower for OP's usecase.
See my sibling comment for a better format selector.
> otherwise download the best available
This will potentially download much higher than 720, if 720 is not available. Probably better to go lower for OP's usecase.
See my sibling comment for a better format selector.