The NX was based on the B14, so roughly the same as a Sentra of the time. I don't see a RWD conversion as plausible... but a FWD VQ35DE swap from a Maxima works Yes, it fits, and it is a fairly common swap, believe it or not. That or the easy SR20DET swap from a Pulsar, as Darkshine5 said.
It isn't wallowy... all 90's Nissans tend to be on the stiffer side of the spectrum for city cars.
According to the 1992 Road & Track magazine, the NX2000 was rated as one of the world's best handling cars against such competition as the Acura NSX, Porsche 911, Nissan 300ZX, Mazda Miata, and Lotus Elan. I find that claim dubious simply because of the fact that she's front wheel drive, but I'll believe she's one of the best handing FWDs in the world. I've had a '95 Altima, and have a '00 Altima, and they have simply amazing handling for being a cheap compact sedan. Also, since when was the 911 considered a good handling car? She's rear-engined. That is a can of nope for me. So are pop-ups... or air-brakes as I call them.
Right as for swaps... um...
I wonder if a Nissan TD42T4 from a bus will fit into a 240SX or the old 240Z. 160hp Diesel 240 anyone?
The gas TB48DE from a forklift or Nissan Patrol is a better option though. 248hp.
I kind of doubt they'd fit though... too long.