My struggle is that I work on lots of systems, sometimes ephemeral/temporary systems. There is no easy way to "sync" customizations, so I adapt to defaults.

Even basic things like how shell history is managed is very annoying to configure every single time. if only it was as simple as cloning your private github repo to ~/.config.

I use a very customized emacs/evil setup, and before that a very customized vim/neovim setup, but I've never had trouble jumping onto systems where only plain Jane vi is available. I think it's because of the color scheme, or lack thereof, that I don't have any problem automatically switching. If I don't see my color scheme, by fingers just automatically use vi compatible bindings and I don't find myself expecting my other customizations to be present.

Maybe not everybody can switch so easily, but I think it's worth trying out. (One change that absolutely does trip me up is capslock->control. If I try using somebody else's computer, I constantly enable capslock by accident.)

Cloning a github repo to ~/.emacs.d is how you can cart around your Emacs config. I've been doing this for years, and it works nicely. For things configured by files that live in the home folder directly (e.g., shell - and looks like Nano would be similar?), I've got another repo with a couple of install scripts that create symlinks to the version-controlled files. I don't love the extra steps, but I've found this works pretty well too.

Most of the time, I can manage without, but every now and again I've needed to do some thing or other, and I've been grateful to have my own preferred setup rather than somebody else's.

Check out Chezmoi (https://chezmoi.io). They even offer a nice comparison table for alternatives.

I don't really sync my config. I just scp or wget files when I need them. I have some config as gists, as snippets in my notes, as public files in a webserver under a subdomain.