Good queston!
I have re-laced a few wheels and found the guidance regarding torque interesting. Some sources have specified a torque value, others have suggested listening for musical "note".
I decided on listening to the "ping" of a wheel I thought to be factory set and set my wheel to the same "ping". Frankly, given the difficulty of measuring the torque applied to a spoke nipple, the "ping" approach seems reasonable.
Playing by ear here,
HTH