While it is true that USB does not rely upon the streamers clock, it seems to me that you want a good DAC clock for stable sampling of any input.
Is a femto clock important if you aren't using asynch USB?
I am considering buying a used Wyred 4 Sound DAC2 DSD se for streaming from my Bluesound Node 2i, and the seller told me that this DAC2 se is one of the early ones that does NOT have a femto clock. My Bluesound does not have USB output, so I won't be using the USB input on the DAC2. My understanding is that the femto clock is mainly useful to sync up the digital stream from a computer; is it likely to make much difference if my source is a streamer and the input is SPDIF?