The diff between themed and unthemed Redux is just a few bits of appearance: statusbar icons, glow colour, spinner. Not much else.
That apart, actually most AOSP ROMs look rather similar. They may come with different included launchers, but stick Launcher Pro, Go Launcher or whatever on and you can make the same look on any of them. The main differences are in the level of additions and customisation: Redux is perhaps simplest (in part because the dev has been busy for a few months, in part by design), Oxygen has a few more tweaks, CM7 more, and GingerVillain is based on CM7 with different custom kernels, default settings, some additions. Best advice I can give is to try some of them and see what you like. I'm currently running a stripped-down version of one of last week's CM7 nightlies, but I've used all of the others I've named, and could happily work with any of them (and doubtless will use some of them in the future).
One thing to note with CM7: if you want a2sd or google apps (e.g. Market) these are separate add-ons, not included in the ROM. People often get caught out by that. The others include these, though if you want dalvik cache on sd-ext you have to apply an add-on for Redux and Oygen, and type a command on GV.
