Balance currents are much lower than charge currents so any voltage difference will be in the noise. For example, my i306B balances at 300mA. I know some of the newer charges may have an amp or two for balance, but still probably negligible voltage difference. You cam estimate it yourself by looking up the resistance per 1000 feet for the different gauges. Assume 1 foot and 1 amp. V= I*R (ohms law). You will probably have more drop in the balance connectors than in the wire.

Even 20AWG is probably overkill for balance leads. Note that balance leads from progressive are made with 22 AWG.
https://www.progressiverc.com/balance-extensions.html