In 1. are you referring to the GP Sections (rows)? If so, nope, it’s all BB. I was more familiar with BB than the GP Sections as this is the first live site I did with GP.
As for 2. I do not use a child theme for GP as I make no changes or additions to any of the theme files, notably functions.php. I do use Tom’s fantastic Simple CSS plugin for CSS and of course, that is update-safe. I specifically asked Tom about this but I am too lazy to look up the post 🙂 His reply was basically what I am doing; if it’s just CSS, then no, a child theme is not necessary.
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