Yes, all NOS DACs are R2R ("multibit") designs. They are multibits that are non-oversampling.
There are also a great many multibit DACs that are non NOS.
I own one of each: Audio GD NOS 19, the non-oversampling variant of this standalone multibit DAC; and their DAC-19, the oversampling variant. My preference is the NOS 19, but they're both excellent, fully featured DACs.
Multibit DACs have truly changed how I hear digital. Yes, they sound more relaxed, organic, and "musical." But whether they are "warm" or not is one of those "how many angels can dance on the head of a pin?" distinctions. What I've found is that when one's digital signal is NOT bright, edgy, overly emphasizing transients, and conveying bass in a weirdly exciting yet ablative way (hard-hitting, deep, but not timbrally rich or faithful to the source instruments)--the music often does sound "warmer," but that's mostly because it's no longer hyped in the manner of many delta-sigma DACs.
Some DACs, just like some solid state preamps & amps, are voiced to be "warm." But even then, their interaction with speaker loads is not exactly predictable. For example, a warm SS preamp + a warm pair of speakers may synergize in unexpected ways, with the result being more apparent resolution (yet not tiresome or peaky sound). In general, "warmth" in SS devices is less predictable than it is in tube preamps or amps (I've owned both and know that delicious warmth well).
Net/net: to my ears, a NOS multibit DAC sounds more relaxed in every way...yet not at all suppressed or undynamic. Sans that delta-sigma spotlighting of transients & treble, it's easier to hear the actual instrumental tone/timbre and layering of instruments...
Ultimately, that apparent "detail" from delta-sigma DACs is just another unwanted sonic filter that tends to obscure the music.