You cannot convert an installed system into an iso file in an easy way. The tools that you link to have been used and can be used, but they are not easy to to use.
That said, I can describe a method that is much easier:
Ubuntu OEM install
- Create the system that you want to distribute by installing a fresh system.
Treat the installed system (that you want to distribute) by installing program packages, tweaking the system language and other settings and maybe adding desktop files and other common user files according to the following link,
into an OEM install system.
Distribute [compressed] cloned images (img files) to the end users. (This is how systems for Raspberry Pi are distributed.)
When an end user installs the system, the user ID, password and computer's network ID will be created so that they will be unique.
An Ubuntu OEM system is an installed system, which is portable between computers, much more so than Windows, but not as portable as a live Ubuntu system made from an iso file.
This will work, if the computers are fairly similar, and particularly if no proprietary drivers are necessary. So if your computer works best with some proprietary driver, typically for graphics or wifi, you had better not install it and rely on the built-in linux drivers. The end user can install a proprietary driver if necessary and maybe some boot option if needed for some hardware, for example
nomodeset for newer and more powerful nvidia graphics.