Backup and iCloud

Correct. But, notes and contacts are not part of the iPhone backup in iCloud. Learn more about what iCloud backs up at https://support.apple.com/en-us/HT207428

A backup to your computer will create a full backup of the device. Review this guide: https://support.apple.com/en-us/HT204136

The iCloud backup has never backed up notes or contacts. Those are typically tied into an email account of directly to your iCloud account. So, they are essentially always in sync. A full backup, one you make to a computer, effectively backs up your entire device and everything on it. If you're concerned about potential loss, multiple backups is always a good idea. I lost a term paper in college once .... never lost anything again. So I backup a lot....

Regardless. Connect your phone to your computer to make a full backup (just in case).

Then, toggle off iCloud backup; since it's not backing up contacts and notes anyway.

As long as you have the services you wish to sync toggled on, you'll be fine.

Check to make sure your iCloud backup is turned off. Settings > AppleID/iCloud > iCloud > iCloud backup