Hi, yes that is the sort of order. For clarity:
GeneratePress is used for the Theme styling
Elementor should be used for building content
Custom CSS styling should be performed after.
Woocommerce is one of the more complex plugins to style.
Their selectors are highly specified and therefore your custom CSS needs to be more specific or worst case resort to using !important.
If you are building Woo with Elementor Widgets you are adding more elements to the page that also need to be considered, again further complicating the process.
If there’s anything specific you need then we are always willing to help