He talks about ADI-2 FS which is a different product compared to ADI-2 Pro / DAC.

Hi Peter,
higher SNR does not result in better sound.
SNR levels are for all products on such a high level, that your ears won't hear any noise.

In a blind test you will most likely not recognize a sound difference between those products.
Maybe subtle changes in stereo panorama / depth if you have very good gear (monitors).

If you have good ears you might notice small subtle differencies between the different D/A filters of the ADI-2 Pro / DAC. Mostly between "NOS" (because of the Treble falloff)  and any of the others.
Selection of different D/A filters this is not a feature of the ADI-2 FS.

The differences are very small. Get one and check yourself.
Instead of getting an ADI-2 FS you could consider to get perhaps ADI-2 DAC FS if Pro is too expensive.
But you can also simply stay with the UFX II .. its a solid product and UFX+/UFXII got both an overhaul of the analog section compared to the former flagship interface UFX.

What is the point of this comment?

I hear differences between NOS and the other filters. That's still relatively easy. I'm not so sure about the other filters, although I have noticed a slight preference for a particular D/A filter while listening.
Ultimately, I just wanted to point out that the ADI-2 FS has no such filter switching capability.

And this thread is also not about what you hear or what I or you think you hear or don't hear...

He apparently intends to refine his sound, at least that's how I understood his posting. The best way to do that is to listen to the equipment for yourself in your own space, because each of us has different ears, monitors and especially different rooms.

Personally, I would tend to buy at least an ADI-2 DAC FS instead of the ADI-2 FS because it has many useful features and the price difference between these devices is not that big at €267.
Dynamic Loudness, Auto Reflevel, PEQ, Extreme Power KH amplifier, four different Reference Levels are already nice features.

But now wait and let him have his say first. If you think you still have to lead any discussions on the subject, then save it for later, at such an early point in the thread is not rather conducive.

In our world of online order/purchasing it should be no big deal for you to get one and to find out in your environment and with your ears. Ears / tastes can be so different ... but I would try the ADI-2 DAC or Pro FS, not the ADI-2 FS as it is missing all interesting features of the DAC/Pro series of devices.

Didn't say that, I just mentioned it for completeness because most people aren't that familiar with the differences between the products.

Is so high nowadays, these differences can not be perceived.

And yes, I have also asked myself what the decisive criteria are for a very good and above all spatial / three-dimensional sound with good localization of voices and instruments.

It is m.E. not SNR, that is only a "side effect" of increasingly high-quality components.

I suspect it has more to do with the DAC, the correct control of the DAC chip and with the timing / board layout. But that's just a guess.

Of course, the speakers, all components in the signal chain are also important and it is certainly not bad that in the RME design the clock is refreshed again and jitter is taken out and ultimately converted with the local clock D/A.

But a few dB SNR do not make the cabbage fat, you do not hear that anyway. This is the noise to voltage ratio. Do you hear any noise there ? Well, I don't. No matter how the volume is set.

FS clock has not been implemented to all RME devices yet.
It was newly introduced with the ADI-2 DAC FS, then it followed for the Pro FS and the other products got it.
Babyface Pro FS, AIO Pro, UCX II.

But the common sense is so far, that you get measurable higher SNR but that this is not audible.