i think a reasonable assumption as to why the lumin u2 mini sounds superior (’more saturated sound, cleaner treble, etc. ’) than a node, as a streamer source, is because the lumin manages noise management/filtering much better, and allows for an upsampled digital feed so that the downstream dac can do its job better in putting the analog music together better...
the good sounding zenstream (with clean external power supply) does very well on the first aspect, don’t think it does the second