Disabling features in 2.7 and 3.0

[Ritmo2k]

On some of my 2.7 clients in my test environment the mirror doesn't even appear, some it does but unconfigured?

Can someone also help me definitively answer a question about where to completely disable the various 'mons in 3.0 using the configuration editor? In 2.7 I just did it at a client then exported the config out, and some stayed greyed out, while others stayed red?

Thanks for any pointers!
jlc