I think you have some good points here but personally what I have learned is to test your keywords and if the rank or not using something like that tube buddy explore option.

For the best ranking videos you need to focus on making something unique that people search a lot without a lot of competition. If something is hot right now get it out right now. We were the 11th most trending video in our country at a stage and it was because we were the first to put a up footage of a natural disaster.

The thumbnail is important because the algorithm takes into consideration how much you video is clicked on and how long people watch before clicking off into the suggestions. This is directly related to ranking.