Non-Oversampling (NOS) vs,

My only experience with upsampling DACs is a Benchmark DAC3 and a Chord MOJO.

With both I prefer the upsampled sound from redbook sources. 

Maybe it's placebo but I hear more detail with upsampling through these DACs.

An upsampling and filtered DAC will measure much better on paper. That's indisputable.

My experience is that either type can sound good, however, my non-oversampling, filterless DAC sounds more like analog - less fatiguing and less "glare" at the sacrifice of some detail.

Depends, converting redbook the 2R2 Multibit Holo Spring dac, sounds far better on NOS than it does with OS, and you find that goes for most R2R Multibit dacs that can do it.
I'm not into Delta Sigma dacs "trying" to redbook so I won't comment on those.

Cheers George

OP>
I am just trying to better understand a NOS DAC vs one that upsamples.

I’m wondering myself how great a part this plays in the final result?

I mean after all, does this really matter somehow?

I believe regardless a dAC be an OS or NOS DAC, there is more to this than the philosophy or approach being lent to the solution.

like the OP alludeed to, as such, EVERYTHING in the dAC build and implementation has to be considered as a ‘WHOLE’, despite the OS or NOS digital side of the affair.

as I understand OS DACs some sonic aberations are attenuated or ameliorated outright via up sampling the rate. the other approach handles things differently, of course.

then to, some dACs deal with sonic issues on the analog side.

doesn't that all by itself sort of make the design argument nonessential?

for eX… lets say you got to hear similarly priced but not exactly, two dACs. one of each design, and in your own rig.

in the end, things were close. very very close. its come down to a coin toss.

the thing then is cost. Right?

one must stay focused on the overall, or end result and not merely at which way they went to achieve it.

it do make for some interesting debates though, from time to time.

if the dAC has the short list of options I desire, I can afford to buy it, and its a decided boost to the sQ in the system, I could care less if they got blind squirrels juggling knives while jogging on a treadmill inside the thing.

well, so long as I don’t have to feed or clean up after them, and they maintain their hygiene.