I'm not sure if I agree that INFJs are low maintenance... but rather a different sort of maintenance compared to ENFJs. Much agree with cascade's comment on Fe emotionality. Extroverted ENFJs have a tendency to let others know about their moods more often than INFJs. That is not to say INFJs don't having fuming moments. They just try not to let it go in front of the general public. Instead they vent in private or with people who they feel close to one on one. The need is focused on a few selected individuals, so if you're merely an acquaintance, INFJs will seem low maintenance.
Re: switching off auxiliary function
Yes, you can turn off auxiliary. But it's not recommended to just skip on over to your tertiary. Instead you should supplement with axuiliary shadow.
From my personal experimentation. Fe is easiest to shut off if I use Ti with Te. I still get Fe making snap judgment on things, but I let it go to analyze the problem with Ti, then ask what's the most effective solution (Te). It's good to have an external balance to prevent myself from being locked up in thoughts. Hence the need for Te in place of Fe.
For ENFJs, I would say the problem with turning off Ni would be Fe running wild. To react without thought. In this case tertiary Se isn't going to help. Because it's just giving Fe more fuel to go nuts. Auxiliary shadow (Si) pairing would help to slow down thoughts. Think about the consequences of what you've done in the past to rein in the impulses. Then Si -> Ni, what does current and past events remind you of, think about what things you can do to break up tension. Use that silly Ni imagination to channel pent up energy.