Back in the day when a lot of things things were capped at 8 characters, my uncle used to work for a company where they had (first 7 letters of last name) + (first letter of first name).
At least until they hired a woman named Margaret Manspera. Luckily, mansperm@company.com was spotted in advance, and she was given margaret@company.com instead.
Move all your heavily modified config files into a git repository and host it somewhere. Then symlink all your config files to where they should be with ln -s ~/.config/whatever ~/gitrepo/whatever. That's how you preserve your important configs.
You can easily get a list of your installed packages (which you can keep in your repository) with apt list --installed > packages.txt. You can then format that list to one you can install from with sed -e "s-/.*$--" <packages.txt (or something, i don't have apt, can't test it fully).
In fact, if someone here is more familiar with apt, please find a way to filter out packages that were not explicitly installed and reply to this comment with your solution.
This supports my claim that EndeavourOS is a just-works custom Arch install, and a brilliant one at that.