Found one locally for $695 in 98% condition. I have read on other sights that parts are unique to this rifle and are not easily replaced. I have also read that some suffer from improperly heat treated metal parts, hence being "soft."

Any truth to this? How are these rifles compared to other AK47 rifles in terms of quality?

Any opinions on these rifles?

The nhm 91's are good to go. The only part differences would be the length of the barrel and the interesting fsb that accommodates the bi-pod. Some models have a rivet on the mag-well to fit notched ak mags. Easily removed with a file/dremel.
Nice rifles..I love the longer sight radius..

Big +1 on sight radius.
Very good ak imho.

If i came across the rifle you describe at that price, i would try to dicker on the price because that's me.
If they don't budge on the price,  I'd definitely buy it for 695.
Does it have the original bipod?
I think that's the " parts not easily replaced" category. Not a big deal honestly, to me.
Solid chinese ak, imho fair price, but im no expert.

I carefully converted mine to pistol grip configuration and i love it.

Just throwing an old link out there, to give a visual see nhm91

With these Norinco rifles there was never a worry of "soft parts".  The only place that came from were the "B-West made in the USA" receivers... These are the ones to stay away from, but ones IMPORTED by "B-West" are GTG.
I had an NHM91 and they're great rifles and they all had "straight cut" receivers so other stocks will fit on them no problem also, as compared to some of the "slant cut" MAK90's.
The Chinese AK's are some of the best on the market and are getting harder and harder to come across since the last time they were imported was in 1994!

I sold my NHM-91 back in the mid-2000s, when I was strapped for cash, and I really had no idea how hard it would be to get something like that back.  I regret it to this day.  It was a 20" barrel version, with a polymer Dragunov-style stock (not sure the brand).  It was really, really cool, and just a blast to shoot.  I love my AR now, but dang it I wish I had that rifle back!