man iwconfig
...but seriously, most all those options are eventually passed to iwconfig so the man should guide you.
before messing too much with wireless.opts, make sure it's being read and used by your system by adding a logger statement to the beginning of it, eg: "logger wireless.opts is being read", then check your log to verify that on a cardctl insert the wireless.opts file is being called. On a couple of my boxes it never gets used.