If you don't back up your iOS devices to iCloud, but you still use iCloud to sync your data between your Mac and iPhone–does Apple have access to that data?
Or do they only have access to data that is saved in your iCloud backups?
to define it very simply:
you can group your info into 2 groups
1 info synced (put onto) apple's servers.
done through enabling iCloud syncing parameters for individual apps that you select.
2 backup info (backups of yr entire iPhone's apps and their data) to apple's servers.
done through enabling iCloud Backup (you can also chose to do only locally stored backups of yr iPhone's data to a Mac you control and own, and not have it on apple's servers).
1 is what you chose to sync to apple's servers.
you make your choices in Settings/Apple ID, iCloud, etc/iCloud/ (various settings)
any app you select here is put onto apple's servers and can be accessed by apple employees if they need to.
there is a legal process that apple does follow to turn over any and all data put onto their servers through this iCloud app syncing. (yesterday or the day before apple just released a country by country, very detailed report detailing this)
2 is generally referred to as a backup process that ostensibly is in place in case you need to restore the state of yr device in case you need to get yr info back to the way it was when you did yr last backup.
most recently the news surrounding this is that apple has chosen to not encrypt this info so that (presumably) it can be made accessible by law enforcement while at the same time apple can publicly maintain its stance that apple itself will not decrypt info that is yours when it hands it over to law enforcement (meaning: apple will not make any backdoors or decrypt yr already encrypted info). (it wasn't encrypted before, so it doesn't have to decrypt it, thereby maintaining its marketing strategy).
in all of this there are two types of people:
1 people who only need to worry about hackers and growingly sophisticated software that can intercept yr info while in transit to others (Message data, Photo data, Mail sent via iCloud, etc etc)
don't worry! a lot (but not all) of the info is being sent through end to end encryption that maintains its security.
as long as you use a VPN and maintain vigilant anti-phishing web practices, you are safe, or, as safe as you can be in mobile digital tech.
2 people who worry about law enforcement or Home Land Security etc etc.
no comment.