1. If you are using sony vegas, there's a built in feature that allows you to record while watching the video, so you can commentate it as you watch in on vegas. If you're not going to use vegas, you can use a program like audacity and record your audio while watching the video.
2. If you have a video over 10 minutes, it will monetize it differently, and they'll get another ad in the middle of the video, meaning more money.
3. Banner is really something you should worry about until further down the road in your youtube career. if you are first starting off, you can have a basic image and if people enjoy your content, then you can start making your channel more professional.
4. It really depends. Let's say you're making csgo content, and you want to speed it up a little bit into the next kill in a round then time lapse would be okay, but in almost every other situation, a transition is better.
5. Yes. Monetize videos with ads. You're putting in effort to make the video, might as well make a little bit of money from it!
also, if you ever need help editing / recording or any of that stuff, feel free to message me. It's what I really enjoy doing so I'd be more than willing to help!