How Config IMCE in Settings.php I can not find any document about it

You can get the values based on the settings form to overhide IMCE settings like:

sites/default/settings.php

$config['imce.settings']['abs_urls'] = TRUE;
$config['imce.profile.admin']['conf']['folders'][0]['path'] = '.';

But, I do not like this solution, because, the form show an information, but another will be run

However in Drupal 8 this not will be reflected in IMCE form, but if you show the global settings with:
\Drupal::config('imce.settings')->get('abs_urls')

you will see this settings

See: Configuration override system