Default setting is to allow unit automatically choose suitable channel. It is possible to set a channel or list of allowed channels.1) there is free channel auto-detection for 802.11n 2.4 GHz and 5 GHz
No idea about that.if so, according to what algorithm (CCA or another) and with what frequency - once every hour or somehow
There's a setting to do that. I never tried it so I can only guess that it actually works.2) for 802.11n 2.4 GHz and 5 GHz, is it possible to set "N-only" mode
802.11n does not mean channel width of 40 Mhz only...!Did I understand correctly that only 20/40 MHz can be set in RouterOS even if all my clients are 802.11n ?
I saw that in OpenWRT or DD-WRT I can set the channel width to only 40 MHz.