It is simple if you think about it.
Remove packages you do not want and replace them with your own package/configs
There is nothing more to do.
And then you can still enjoy an up-to-date Calamares, bluetooth, printing and all the rest ArcoLinux provides but it becomes your personal iso.
How to change the look of the xfce4-terminal and make a package
After watching this video you will understand the workflow behind creating your own look and feel.
You can add so many other things related to XFCE4.