Thank you for your post.
You could use your Picoscope to measure dwell (coil-on time) in ms if this interests you. In terms of 'optimum' dwell this may be harder to determine.
With conventional 'points' ignition, note that as engine speed rises the dwell time remains the same (set by the points gap) but the time is reduced. As a result at high engine speeds, with less time to charge the coil a lower kV spark was produced.
As things have moved on, many vehicles today employ constant energy ignition systems, using fast charge, low resistance and inductance coils that are under tight control of the PCM. By monitoring the voltage drop across a high power precision resistor in series with the primary coil, current is controlled and within limits, secondary kV is kept constant across the rev range.
Engine developers spend many hours getting the ignition mapping optimised for stock engines and so I would have thought there was little to be gained here in terms of tuning potential.
There are many text books available with more on this subject. We stock a particularly good one here: