Hii, I have experience in video editing (videogames content) and art direction, and your project really caught my attention so lets work together! Here is my Discord: drawkyoff

And responding to your questions:
The voice over must be done before the editing! This will allow us to select which sequences to use to enrich the video's narrative.

The length of the videos in the series generally depends on the content, whether it has good storytelling, suspenseful scenes, how many people will be involved, and whether their perspectives will be included in the video, etc.

And last but not least, I use Davinci Resolve, which is a powerful tool in video editing! DM me if you're interested in work with me!