A Softaculous backup or backup plugin are only going to backup your sites files and database.
A (full) cPanel backup is going to backup your site files, database, and other things such as your email accounts, emails, forwarders etc. Granted you don’t have to do a full cPanel backup, but that retains all settings inside of your cPanel account.
If you’re just interested in backing up your site files and database then Softaculous or a plugin would be fine.
Yes, Softaculous is one click auto installer which installs scripts in one click and can maange your sites like backup , clone, import, upgrade etc, Softaculous only backup your sites which is managed by Softaculous which includes the files and databases.