@m.fessler 

Hey

If you are using a controller then generally this works fine on AUTO and there is little reason to change the power level manually.  

After hundreds of WiFi installations, I can honestly say I have only manually set the power levels for 2 - 3 customers at most, its just something that isnt required anymore.

Channel wise, totally leave 2.4 on AUTO as it will adjust to suit the airspace at that time.   Knowing 2.4 its likely to change every day so manual doesnt offer any real advantage here, just hop around to avoid on auto.     5ghz I personally do use manual channels, usually DFS however

In answer to your question, scanning of the AP is done at boot.  However if you have a controller AI WiFi can do the scan on a schedule, I personally have 2.4 on a daily schedule so it checks at 4am every day.. 5ghz i dont and manually set.