I think new Unicomps, like vintage Model M's, are actually 2KRO (not counting modifiers). Check the wikis to verify.
I've owned a Unicomp SpaceSaver and a Model M, and they look and feel identical to me aside from the logo, the Windows key, and the cable. Those more expert than I will be able to describe the subtle differences, but a Unicomp keyboard really is a Model M. Same design, same molds, same production machinery even. They are large, loud, and heavy, and yeah they creak. It's all part of the charm.
I enjoy playing Starcraft on my M, but I can't speak to FPS games. The low KRO might be an issue there.