Is it good usability to use arrows (pointing down) with anchor links?
Arrows are not necessary, more specifically arrows that are pointing down are best suited as an example: an accordion element that expands and collapses vertically.
However depending on the amount of content, consider using a functional element for clarity. For example:
- Section A
- Section B
- Section C
Should the arrow be on the left or right?
Should the arrow be included in the hyperlink (and thus be underlined?)
It should be outside hyperlink. This type of element is used as a visual aid.
Should the arrow be an image that is also hyperlinked?
No for the image and no for the hyperlinked, try to stay away from using images when the same can be achieved with HTML or CSS.
For a ordered numbered list use (like the example above):
For a bulleted list use: