If your iPhone and iPad share the same iCloud and Apple ID, will their respective backups overwrite each other? Really appreciate any help. Thanks.

Hello, backups don't overwrite each other but get updated. If your devices share iCloud Photos, your photos will be synced across these devices. However, individual app data is tied to a backup for the specific device. If you tap on the 'Backups' section in iCloud on your iPhone or iPad, you can see a list of individual backups for your devices.