MainWP supports customized /wp-admin/ installations. If your child sites have custom /wp-admin/ path, sites will be able to connect to your Dashboard.
By default, MainWP Dashboard will try to reach http://url.com/wp-admin/admin-ajax.php, in case it fails, it will retry with http://url.com.
MainWP supports renamed wp-login.php installations. If your child sites have a custom login URL, sites will be able to connect to your Dashboard.