adevlunix We aren't far off from the normal FHS. The notable exceptions as you pointed out are related to statelessness. With the exception of systemd, all stateless packages have their default configurations in:
/usr/share/defaults
These configuration files may be overridden or supplemented by user-created files in /etc. Any non-stateless packages also still have their configs in /etc.
systemd related things can be found in /usr/lib64/systemd or /etc/systemd
The only other thing that comes to mind is that /usr/lib is a symlink to /usr/lib64