I have really pretty bad luck with chaeto in my main tank with VHO lighting but it's got to be the lighting because in my connected refugium all I run is a little 60 watt grow lamp from lowes and the chaeto grows like mad.
As for caulerpa, if you're looking for something that a tang might keep in check for you I'd definitely look at the miniature type grape caulerpa, my tang loves it, but when I have enough he doesn't get around to decimating it.
If you have a tang and don't want him to eat your caulerpa, get sawblade caulerpa, my tang won't touch the stuff. I'm sure roughage preference varies by tang type but mine is a medium yellow tang and that's what I've gathered from him so far.