I’ve always done this with overlay filesystems and repackaged configs.

SystemImager and rsync modules did what Kickstart and CFEngine could not: take me from COTS to Custom in this lab or one in another country.

Kiwi did a pretty good job for a bit, but locked you to SUSE.

Nix seems like a runtime environment rather than an OS, but I haven’t spent the sweaty hours with it that I have the others.

Ansible and Debian work equally well on a laptop VM, Cloud Provider or colo rack.