Checking for CSS & PHP changes during migration

Hello,

I’ve read through the migration documentation and watched the sample video on the Atomic Blocks site, however it essentially says that the CSS and PHP won’t be a step needed for most users, but does not demonstrate the process if one were to need these checked and changed.

My concern is that I have CSS (and possibly PHP) that is tied to Atomic Blocks within custom CSS & PHP plugins as well as theme files made by developers. I am unsure what the search tool does during the migration for either CSS or PHP and whether it would detect coding across various plugins that store CSS and PHP and all theme files.

Any clarification on that part of the migration and how to ensure everything is found and changed would be appreciated. Thank you.