Need advice on lens choices

[Jon Ruyle]

I believe that the extension tube's contribution is primarily changing the focusing distance.

I believe that, too.

Do they change the angle of view as well?

It depends on what you mean. They allow you to focus closer, and when you do focus closer, your angle of view diminishes. But of course if you focus 10 feet away with or without extension tubes, you get the same angle of view.