32 steps? More like 14, and that's just what the base will recognize. The stock throttle only has 11, and the throttle profiles only use 7 or 9 of them (see Dave Chang's book). Even the Progressive controller uses 11 steps, but has a variable resistor for one of them. Using a slot.it controller gave you the full 14 steps, but that's still a far cry from analog. So yes.. oXigen will be a marked improvement over N-Digital.
PC Lap Counter has fuel based on throttle usage. At least, that's how it does it for other digital, so I'm guessing it does it also for oXigen. It's adjustable, but essentially the more throttle you use, the more fuel you use. A careful driver is likely to use less fuel for a comparable lap time (or better) than a reckless one that pins the throttle as much as possible.
I haven't read the whole Ninco section of Dave's book, and Cesar can back me up or point out my error, but I don't know of anything that N-Digital does that oXigen doesn't do better.