As for a disabling JustCode features, the add-in manager can be used for that, for the instance you are running, without having to restart Visual Studio.
On the other hand, I've had the same questions, about disabling the extension itself (I still do). For now, I rarely have to disable JustCode, as it works fine for me. The maximum of RAM it has taken, on one my instances of Visual Studio, is 300MB.
In order to optimize memory consumption, I often manage settings in order to enable only use the necessary options.
There's a feature you can use to centralize the settings if necessary also :
hope this helps,