Hmm, I've never done this. In terms of config files, are there never any breaking changes between versions? Like ..is a v1.0 config file always guaranteed to work with v2.0 and vice versa? I guess and a related question - what is the best way to determine if an /etc/ config file isn't required?
It gets more exciting the further you drift - e.g. if you're going to Debian buster, or something more significantly different like Fedora/RH, you'd probably want to cherrypick config changes from /etc, though /home should be fine(tm).
you start culling packages with apt purge, that should remove config files too, and see what breaks, if nothing, well, try to push your luck further.
also with dpkg -S /etc/some/file you can see which file belongs to which package and target that package
usually on a server you know what you don't need. it's a bit more trial and error on a desktop. (because those can break in a lot more fun, unexpected ways, harder to know what is needed)