How to set up iPad and phone to not be connected

Assuming that both iPad and iPhone are signed-in with the same Apple Account (recommended), you simply need to disable the Apps and Apple services that you don't wish to synchronise via iCloud...

On iPad and iPhone:

Settings > [Your Name / Apple Account] > iCloud > [Saved to iCloud] See All >

Enable or disable the Apps and services that you do or don't wish to synchronise via iCloud. Consider that, for convenience you may still wish to synchronise one or other device with iCloud - or just some services - with iCloud. Apple services appear towards the top of the list - with Apps appearing lower down the scrollable list.

Not connected in what way? There are many ways that an iPhone and iPad will share content.

• If they share an Apple ID then you can share selected contact (or not share it) by going to Settings/[your name]/iCloud and turning off switches for the content you don’t want to share.
• You can share calling and phone information in settings on your iPhone. Go to Settings/Apps/Phone/Calls on other devices and turning it on or off.
• You can share or unshare messages by going to Settings/Apps/Messages/Send & Receive and checking or unchecking devices.