Is it ok to turn off iCloud back up

Your data will not be deleted, but they will not be in iCloud. There are two types of iCloud data: ones that are synced, and ones that need a backup. Here's the article about what iCloud backups incudes: What does iCloud back up? - Apple Support

lele199 wrote:

Is it ok to turn off iCloud backup

Sure. But that also implicitly means the data on your iPhone is of little or no value to you, and you are willing to start over without restoring and without recovering whatever data was on the iPhone. It also means you are one dunk or drop or ding or loss or theft away from that data loss.

Word to the wise......if you do not have a backup....you will at some point really regret it.