Does channel choice have much effect on ac wireless as opposed to standard 5GHz networks?
Doesn't it really depend on how much bandwidth you ask for your selected channel? ie 20MHz vs 40MHz vs 80MHz
With 20MHz bandwidth, you get channel 36, 40, 44, 48 on cheap consumer kit (ie does no automatic radar detection); all other channels require the radar detection, so tend not to be quite so readily available.
With 40MHz, you can end up using 36+40 together or 44+48 together.
Wireless N offers the ability to use 20MHz and 40MHz channels.
The difference that "AC" routers bring to the party is that they allow 80MHz channels - which use all 4 channels to bring those heady speeds (433Mbps with 1 stream, or 1300Mbps with 3 streams). I guess you need all 4 to be free, and to specify an 80MHz channel.
Any suggestions for a free program to detect such networks and show the channels?
Do you have an android phone capable of 5GHz? If so, you can use the "WiFi Analyzer" app