The "icewm" package is the same, whether installed as part of Light, or not. The difference is in the metapackage "icewmvmods", which installs during Light installation if IceWM installation was selected (the default). None of the application binaries have been altered. The difference lies in the config files in icewmvmods, and some from the package "VL_Theme-Light". I believe the jwm setups are only in the Light Theme package, and aren't available standalone from the repo.
You can take a look at the actual customizations by issuing
less /var/log/packages/icewmvmods-<tab-complete> then looking through the files listed; same thing for VL_Theme-Light.
The "icewm" package itself is not a standard release at this time, but rather a snapshot of a recent commit to IceWM's "official unofficial" repo,
https://github.com/bbidulock/icewm . It's expected that we'll return to using a standard release from that same repo sometime in the near future. No great difference is expected when the switch back is made. For now, the package version and that returned by "icewm -V" will not agree.
7.1 Light shipped with twm very lightly configured as the fallback when IceWM was not installed. For 7.2, JWM has replaced it. It's nightflier's work with putting Light and IceWM configuration on top of the simple, slim base system provided by the crew that has kept me on VL since first trying Light. And now I'm getting ideas about trying some new things with old boxen, with his JWM setup as a starting point.