stop updates

I have a question regarding the updates of Twenty Seventeen and plugins.
I don’t want the updates, or I want to decide if and when install them.
This because, even if I use a child theme, some of my mods can be changed,
in particular with plugins update.
I found a post suggesting to add in wp-config.php the following line:
define( 'AUTOMATIC_UPDATER_DISABLED', true );

I don’t know if it works for auto-updates (recently no updates) but for sure it does not work for update alerts.
Which should be the correct way?

I just want to check sometimes and decide, not receiving daily alerts.
Thanks