Between Skins and Profiles in Kodi, you should be able to switch between two very different looking set ups in the same Kodi build, yes. If the retro mania build is from an APK (rather than a Wizard), install that first, then Wookie into that Kodi build. If retro mania is effectively another Wizard add-on, might need to experiment with seeing which to install first.
has a bit on Kodi profiles, though you'll need to find the equivalent shortcuts if you're using a different skin