Under advanced wifi settings one can change number of Wi-Fi channels to be used (11, 13, 14). Does anyone have a clue on how does this property affect battery drain? I know it should be configured depending on how your Wi-Fi router is set-up, but maybe one number of channels should be ("defaultly") preferred over another so battery would last longer?
It has nothing to do with battery life; the number of channels is a regulatory issue (for example, in the US, only 11 channels are allocated for 2.4GHz Wi-Fi).
Technically, Wi-Fi is frequency hopping, so the "channel" is a center frequency around which the actual transmit frequency skips. You can't disable that; it's part of the channel sharing arrangement (Wi-Fi would be unusable if every client on the channel transmitted on the same frequency). And beyond that, which channel your device uses is determined by what AP you're associated with, so you have no control over it.