backing up multiple iPhones to iTunes

My wife and I both have iPhone 8's running latest (currently 14.3) IOS. Of course, we also both each have unique Apple IDs. Can we back up both phones to 1 Apple ID account within the iTunes app, or should we logon to our separate Apple IDs within iTunes to each backup our individual phones?

Also, does iTunes store the backup files(if backed up either on one's local machine or to iCloud) based on Apple ID and phone name? I.E., if using 1 Apple ID to back up both phones, there would presumably be 2 backup files under that one Apple ID vs using unique Apple IDs to back up the individual phones where there would be 1 backup file associated with each Apple ID?