Using option type bridge inside a config interface is deprecated. The new syntax is to declare bridges separately.
A bridge with only one port (e.g. a single wifi AP) is not necessary, but if you start out with a bridge you can easily add an AP on the other band, or an Ethernet port.
That is just plain wrong. Use option network in the wireless config to attach an AP to an interface (or bridge, if the interface has a bridge it will be automatically added to that bridge instead).
That does nothing in an interface that is not WAN.