Does Time Machine backup all users?
Beside this, does Time Machine back up all users?
Time Machine will back up the whole hard drive, including all users on it, unless you have it set to back up only certain folders. Yes. Time Machine will back up the whole hard drive, including all users on it, unless you have it set to back up only certain folders.
Secondly, how does Time Machine work with multiple users?
Time Machine does a full-disk backup which would include all the user accounts since they are all stored in the same /Users/ folder. If Time Machine is enabled in one account, then when that account is active Time Machine (which is set up in that account) will backup the entire drive unless you exclude something.
Use Time Machine: After you set up Time Machine, it automatically backs up the files on your Mac. If you ever lose the files in your Photos library, you can restore them from the Time Machine backup. The permissions for your Photos library may conflict with those for the Time Machine backup.