Good question. Unfortunately the answer, in my experience, is all the above.
I say unfortunately because getting streaming "right" can be a real challenge.
Firstly, what does good look like? In my experience, when digital sounds "right", that means that the upper keys of well recorded piano music sounds natural, same for cymbals.
When a part of the digital chain isn't optimised, then that's where the tell tell signs appear, like digital "ringing" and worse, those upper piano keys take on a "glassy" or "edgy" sound. It totally ruins the experience for me when that happens.
The power supply in digital is critical. I tested this for myself with a zen mini MK2 and I was surprised to hear differences with a good linear power supply Vs the factory wall plug. The Rose uses virtual battery super capacitor approach.
The connection to DAC is critical too. Cheap USB cables are the worse offender. USB generally should be avoided in lieu of AES ideally or coaxial in my experience.
A lot of folks use USB so they can upsample to DSD. Upsampling is usually a path to making the sound more "digital", don't bother.
The WiFi / ethernet is also important but less so in my experience. I also don't hear differences with WiFi Vs LAN. My current setup is X10 Nighthawk router set as a WAP, powered by 5A 19v power supply. Then SFP to my Rose.
One note on streamer connections, do not under any circumstances think that fibre media converters are a good idea unless you use high quality Cisco AOC or Finisar transceivers. I tried media converters with basic transceivers and the sound was totally ruined. Transceivers have a significant influence on sound believe it or not.
Finally, master clocks are least important I would argue. These are also a somewhat controversial topic. They have a subtle effect and need to be of a very low phase noise to improve anything over the internal clock. Clock cables also play a big part here and can make a master clock sound worse if the wrong type and or low quality cable is used.