Multidomain with same files from the site folder

Hi,
if I have a multidomain setup like on https://getkirby.com/docs/cookbook/setup/multisite and I want to have only site specific files in the domainfolders and other else should only managed for both domains omce. How have I to write the array in the new Kirby object?

$kirby = new Kirby([
  'roots' => [
    'index'   => __DIR__,
    'site'    => $root . '/site',
    'content' => $root . '/content',
    'media'   => $root . '/media',
    'assets'  => $host . '/assets'
  ],
  'urls' => [
    'media'  => $url . '/' . $root . '/media',
    'assets' => $url . '/assets',
  ],
]);

Whats the right way for eg. site/plugins?
Is it

$kirby = new Kirby([
  'roots' => [
    …
    'site/plugins'    => $host . '/site/plugins',
    …
  ],

And for what pathes I need the url part? Only for absolute path files?

Best

This only makes sense if you use each folder in /site separately, otherwise /site already covers everything.

All stuff that needs to be publicly accessible via URL, which is usually only media and assets