IIRC WiFi channels are highly overlapping - you need to be a few channels apart to have no interference from other channels. Channel 2 will have interference from channels 1 and 3, maybe even 4. I read up on this years ago and forgot how far that goes; I do remember there's serious overlapping. So that's why I suggested to get a WiFi analyser app and see what's out there and which channels are in use.
Unless you have full control over all WiFi it's probably best to let the device figure out which channel to use.