Is first Ubuntu user root?
When I set up Ubuntu system for the first time, and create first user, will that user be root? I would like to use sudo user, so how to add it if first user is root? Also is it possible to create sudo user withoute root user?
The first user won't be root. The first user will have sudo permissions. So just install Ubuntu and you'll have exactly what you wanted.
The root user will be created behind the scene, but root login will be disabled.