iPhone
When changing iPhone to factory settings, will data be lost on other devices linked via the Cloud?
Question marked as
No, the data on your other logged in devices will be safe on their hard storage.
See here for more information: https://support.apple.com/en-us/HT201274
Also, if you are planning to sell or give away a device, you should remove activation lock first.
See here for more information: https://support.apple.com/en-us/HT201351