Depends what aspects you want to configure - things like color/themes/wallpapers or even the keybinder and whatnot are GUI configurable - the keybinder is a biggy since you can then map a hard key to run a command (such as that KDE right click script - which works great in Enlightenment as expected).

With that said, I have not located a way to modify the menus via the GUI - although such a beast probably does exist. There are quite a few "epplets" that add various functionality.

Now as far as resources used, I never really used Icewm before, but I get the general impression that it is lighter than enlightenment. Speedwise though - I found enlightenment to be very usable. I believe the install took maybe 8megs for the whole shebang, so I'd recommend taking a glance.