You might think of them as a speprate thing, but the customizations you have made are files. You can capture a lot of them just by saving the “dot files” in your home folder (hidden files and folders unique to your user, type ls -la ~ to see what I mean).
Search the forum and you will find a hundred different ways to make a proper backup. I’m partial to rsync but some reading/experimentation is required: rsync - ArchWiki
Other ideas: System backup - ArchWiki