Huh? You can totally change the advanced settings (about:config) for Ironfox. I literally had to do that a few months ago to get a certain feature working for an extension I use cause some javascript and SCP settings were disabled for privacy/security.

Now, I completely understand why you wouldn't want to spend hours tweaking settings and reading Mozilla's source code forms to get stuff to work, so if that's the reason for switching then I get it. But you can absolutely change the config settings, unlike vanilla Android Firefox which doesn't enable about:config