Hi Jodie,
Here’s a video with regards to creating an Author Box: https://www.youtube.com/watch?v=4x6CjGOyagc
There’s no correct way. The layout is preferential.
If you would like to add a background to the author image, you may place it within a Container with paddings, and add the color to the Container Block.
When editing a GB Block, there should be responsive view buttons at the top of the Block setting that should allow you to make specific edits for each view: https://share.getcloudapp.com/xQuwRyRL
Hope this clarifies!