Doug,
1) you do not need the variable control, but if you're going to add it, I would buy the compensating timer instead. They work the same, adjusting the time or beeps for the relative brightness as it changes throughout the exposure, but while the variable controller gives you metronome beeps, the timer allows you to set your time and concentrate on whatever you do during the exposure. My mind easily wanders so the metronome is not so good for me. both units have the dry-down feature as well as brightness control to increase your exposure time if desired.

2) you can use VC filters with either lamp, but will either need to trust someone else's table of filtration and grades, or test to your own satisfaction.

3) I'm not certain of your question here, or if it is one. Let us know.

If you're not going to add either the controller or the timer, it's a shame to waste the sensor in the head. As I have one with (Zone VI branded) and one without it (Aristo branded), I'll volunteer to trade my sans sensor Aristo head for yours. Just trying to be helpful!

I've never checked to see which lamps my heads have Ned. Now I need to investigate!