I think the reason few use the manuals is folks feel they have to read from cover to cover.
I think a good strategy is to read the table of contents, read the topic paragraph for each chapter. Then get in the app, use it a while, then start pulling down the menus, and look up things you don’t understand in the manual using the index.
You can also read online the basic topic of digital video. For example, there is an entry in Wikipedia called Comparison of Video Codecs.
My basic suggestion is: when you run into something you don’t know, let that trigger your creative, curious mind to learn about it. If the source you are trying to learn from confuses you, find another simpler source that explains at the level that helps you.
Another useful method: once you are comfortable with an app, find a super user and give them $50 to sit with you for an hour and give you their perspective. In the manual, all options are treated equally. With an experienced user, you will gain value judgements.