Softest/Warmest digital coaxial cables?

aq cables are just fine, well made, neutral

don't go up their line into the crazy expensive ones (true for any brand of wire)... you are just paying for the owners' home renovation...  :)

as you are experienced in the field i am sure you are aware that electrical transmission of digital data waveforms are fundamentally different than analog ones, where silver cables often brighten the sound, copper ones add warmth etc etc

here is a potentially useful reference -- https://audiobacon.net/2018/08/11/the-audiophiles-short-list-the-best-digital-coaxial-cables/12/

i personally have had very good experiences with cullen’s digital cables as well as those made with belden cables by blue jeans... very cost effective... i do not hear a difference from much more expensive ones i have tried that were ’highly recommended’ in many forums in my digital front end -- in which i have chosen carefully to minimize jitter and other digital artifacts

good luck

harshness and unnatural sharpness in tone from the digital source often a sign of jitter or other electrical noise in the signal transfer

'warmer' cables may just be a band aid for the underlying problem