I have seen people doing SEO for YouTube. Optimising titles , descriptions, tags, hashtags, internal linking and so on. I am not sure what results they are getting by doing so. No improvement in views, subscribers and overall channel growth is the same.

1. Is keyword optimization in Title Description for YouTube videos helpful?
2. How to find out rankings for those keywords?
3. Does number of uploads per day matter?
4. What are the tags helpful for and how to find the right tags?

It will be great if anybody could guide me.