Buckling springs are NOT quiet. That said, my Unicomp EnduraPro is a bit quieter than my Model M, after a day or two of break-in. There is a greasing treatment that can be done to the springs that makes them MUCH quieter, at the expense of some feel, and Unicomp will do it for a charge of $40 (it's rather labor-intensive,) but you also lose the warranty.
As for feel... for Cherry switches, IIRC, black is linear (no click at all,) brown is tactile (you can feel the click, but not hear it,) and blue is audible (you can feel and hear it.) I'll defer to other posters for how they actually feel, as I've not used any Cherry switch-equipped keyboards.
I'll also note that most modern computers can recognize a USB keyboard in the BIOS, so that's not an issue.
(Obviously, Windows keys are a plus for using it on a Mac, so I would stick to either the Customizer 104 or SpaceSaver, not the Customizer 101, if you go with Unicomp.)