iCloud Keychain lets you store passwords and credit cards for all your different logins rather easily. While you can always disable iCloud keychain altogether, you can also disable password and credit card saving not only individually, but on a per-device basis, and only for Safari. Perhaps you have an iPad that's used by other people in your home. You may want iCloud Keychain access but don't want Safari saving every single password or credit card number entered on that specific device. Luckily, you can pretty easily do just that!
How to disable password or credit card storing on a device specific basis
Launch the Settings app on your iPhone or iPad.
Tap on Safari.
Tap on Password & AutoFill under the General section.
Turn Off the option for either Names and Passwords or Credit Cards, or both.
That's all there is to it. Safari will no longer prompt to save or autofill passwords stored to iCloud Keychain for that specific device. Just repeat the process on any devices you don't want autofill to work with for iCloud Keychain.