cios_fix.wad is just something you would install to be ABLE to install cIOS in the first place. If you have the trucha bug in some IOS or a cIOS already installed to IOS249 then it isn't needed at all. Actually I don't think it is ever really needed at any point in time anymore. Now recent cIOS installers let you choose what IOS to use when you run the installer so instead of using an IOS with the trucha bug to install cios_fix.wad and then running a cIOS installer, you should be able to just run the cIOS installer and use the IOS with the trucha bug to begin with.
And yea cIOS is basically needed to do most anything like installing wads (though if you have another IOS with the trucha bug you can use that one instead) and playing backup games, or using a usb loader.