Just an insight to GeneratePress.
A lot of what other Themes require a Child Theme for can be done without one in GP.
1. The Customizer is fairly comprehensive for applying styles and setting the general layout.
2. The theme templates and functions are filled with Filter and Action Hooks. In a lot of cases this means no need to create your child own child theme templates to make changes.
3. The Elements module exposes Action Hooks ( and some Filter Hooks in the Layout Element ) via a user friendly interface. So injecting code/content ( including Block designed content ) into a template can be done within the theme.
I primarily use Child themes for PHP snippets, CPT Templates ( where necessary ) and local Font storing.
Hope that helps – happy to help with any specifics.
Once you’re done at the staging, what’s your practice to move it back to the live site? Essentially step 3?
Thats correct.