What happens if I remove a device from my Apple ID?

If you remove the device from your apple id then that device is no longer access to the contacts, images, videos and backups of that particular Apple ID that you removed from your device.

How To Remove Devices from Your iCloud Account | Maximize the Security of Your iPhone

We often use same iCloud account for all of our apple device. Meanwhile have a look at the devices connected you your iCloud account and If you have any device on the list you don’t own anymore, you must remove it before risking your security.

Remove An iOS Device from Your Apple/iCloud Account

This video will help users with the process involved in removing an iOS device from an iCloud/Apple account. This could be useful for a number of reasons. In the Eau Claire Public Schools system, all district-owned iOS devices should not be attached to a personal iCloud/Apple account.

Does removing a device from iCloud delete everything?

Assuming that you never again have the gadget since you parted with it or sold it, you want to remotely eradicate it before you can eliminate it from the record. Content from the gadget is deleted yet none of your past reinforcements are put away in iCloud.