Here a little list of the Utility and tool for video workflow:
You can calculate the duration of a script using this site: http://readtime.eu/
You can create a computer-generated voiceover here:
https://ttsmaker.com/
http://www.fromtexttospeech.com/
https://www.naturalreaders.com/online/
Here a resource for free image bank: https://www.pexels.com/
Youtube sound library: https://studio.youtube.com/channel/UCTp5h-NKoHy-w2wnJcmR5hA/music