The 90-Two was the predecessor to the 92A1. It introduced the recoil buffer designed to better handle .40 S&W. The FS safety incorporated an 'over-center' position designed to prevent accidental activation when clearing malfunctions. Most interestingly it was convertible from 'FS' to 'G' configuration well before the introduction of the current kit. The 90-Two was much maligned for its one piece grip design. The 90-Two definitely deviates from the standard 92 design - frame, slide, safety, grips are not interchangeable - not sure what else.
Personally I'm not a fan of either the 90-Two or 92A1, but between the two I find the 90-Two the more interesting pistol due to the convertible levers. Still, I think the 90-Two is what you get when you decide to let Giorgetto Giugiaro (a prestigious automobile designer) design your pistol, where as the Elite I/II/92G-SD/Vertec G are what you get when you let the Beretta Shooting Team design pistols.
And 90-Two has got to be one of the worst product names ever.
If you want a threaded barrel, G-compatability, ability to change grips, and a standard 'D' spring out of the box, why not just get the M9A3?