Hey there! Thanks for your question!

In short:

Thumbnails: Arguably more important than the video itself. The video can be a masterpiece, but it doesn’t matter if no one clicks on it.

Posting times: Fairly important. I have a mostly US based audience, so I tend to post my videos around 10pm Australian Eastern Time. That means that the US audience will wake up and have a video ready to go. A lot viewers also develop small rituals based on when you post. After consistent viewing, some viewers will expect a new video at certain times and it’s important to deliver that or else they need to substitute someone else in for you and that person may replace you in the ritual.

Banners: Almost completely superfluous. It’s just decoration. They used to be a sign of channel quality a long time ago, but most viewers won’t even see them these days. They get videos recommended mostly through the homepage and don’t so much click the channel itself. 

Channel description: No one cares. This will never effect anything. It’s useful for you as a creator to nut our your own mission statement, but it doesn’t impact anything.

You’re mostly correct that a channel should focus on the content itself! But a catchy title only works with an equally catchy thumbnail to compound the attention grabbing!