Uneven speaker wire runs

If you are going to the trouble of bi-wiring (dubious from an engineering perspective if this will make an audible difference given a low impedance SS amp driving your speakers) then I would go for exactly the same length wires to be safe (after all you are spending a lot of money - so why not spend $200 more and eliminate any doubts/worrries)

I doubt you will hear an audible difference. Electric signals travel at close to the speed of light and speaker cables do not filter the signal very much (unless you have a mis match between speaker impedance and amp output impedance...for example a 4 ohm speaker with a tube amp of high output impedance).