Solved Existing website

It's highly recommended that you use it on a fresh Divi site. Certainly, there are some CSS that might affect your site in some ways, but I would say that it's quite minimal. All you can do is just install it on your site (following the guide) & browser through your site & see if it works fine.

If you don't like how our child theme works with your current site, you can just uninstall it & your site will be back to normal. So, it's safe to install it on your site.

I believe it should work just fine with your site, maybe with some minor CSS fix.

Another thing is that you can skip the import for Theme Customizer, since you already set it up for your existing site.

 

If you just import the Divi Ultimate Library, it won't affect your site. It will just add those premade sections & layouts in Divi Library.

But those premade library items won't work by themselves. You will still need to install the assistant plugin (Divi Ultimate Plugin) to make them work.

 

The plugin won’t break your site. It might affect some styling (but will be quite minimal). If you find the plugin not working well with your site, you can easily deactivate it & your site will back to normal. But I don’t think it will affect much on your existing site, except for WooCommerce pages.