Regarding the length of AES/EBU or coaxial S/PDIF digital cables see the excellent post by Kijanki near the beginning of this recent thread:
https://forum.audiogon.com/discussions/using-a-short-coax-cable Regarding speaker cables and line-level analog interconnects, if the goal is to minimize the sonic effects of the cables the shorter the better.
Regarding phono cables, in the case of low output moving coil cartridges, while it might not make a great deal of difference it is preferable to minimize capacitance by minimizing cable length and/or choosing cables having low capacitance per unit length. See the post by Lyra cartridge designer Jonathan Carr ("JCarr") dated 8-14-2010 in the following thread:
https://forum.audiogon.com/discussions/dynavector-xv-1s-loading-questionIn the case of moving magnet cartridges the sum of the capacitance of the phono cable, the capacitance of the tonearm wiring, and the input capacitance of the phono stage should fall within the range of load capacitance recommended for the particular cartridge by its manufacturer. Obviously this will often require some guesswork, as some of these parameters may not be specified, and some manufacturers of moving magnet cartridges don’t even provide recommendations for load capacitance.
Regarding power cords, see "Misconception No. 7" in the following paper by Shunyata. The importance of their recommendation figures to be dependent on the particular cord, the component it is being used with, and the other components in the system from which or to which component-generated noise may couple:
https://shunyata.com/2016/06/27/power-cord-misconceptions/ Regards,
-- Al