You need to also back up the database in addition to the plugins folder. Not only is information stored in the database about which versions of which plugins are installed, an updated plugin itself may make changes to its settings which is stores in the database.
Without backing up both the database AND the plugins folder, you wouldn’t be able to rollback from a bad update.
Ideally, you should use a staging server for testing updates.
Regardless of whether you use a staging server or a production server, I recommend that you learn to use WP CLI. This makes backups and updates much easier, especially if you need to roll back from something that doesn’t work.
By using WP CLI, you can export your entire database with a single command – wp db export. Then you can zip the entire site (which will include the db backup) – zip -r mysite_backup.zip *.
At that point, you’ve got a backup of your db AND every file/folder on your site from which you could completely restore your site to the pre-update state.
(BTW, you can also use WP CLI to batch update the plugins with wp plugin update --all. You can also use it to roll back an individual plugin to a previous version if necessary – wp plugin update my-cool-plugin --version=1.2.3)