I haven't run a scope output on my Provari, but it works just fine with an inline digital voltmeter, unlike my eGo that uses pulse modulation. With the eGo, it just flashes as the pulse train passes alternately to zero and back to peak voltage. On the Provari, it reads exactly what it's set on ... well, at the 4.0v setting it reads a steady 3.99v on the inline digital. We'll give it 1/100 of a volt and call it exact.
I am assuming from reading different stuff this pulse modulation feature really make the vape. I saw somewhere the provari has this as well as the Ovale V8. I was wondering if these new versions of the Lavatube or the Starfire VV have it?
yes, PWM (when implemented properly, like in the provari v2) does help maintaining a constant vaping experience (voltage) while the battery discharges.
some of the devices using PWM, like for instance the kick/DNA/darwin by evolvapor, even manage to maintain a constant wattage output regardless of the resistance of the atomizer(s) in use.
to answer your last question, recent lavatubes (so-called v1.5) do use PWM for maintaining constant voltage; I had a LT v1.5 and it worked decently, even though its PWM wasn't able to actually deliver the voltage shown on the display, under load.
hope this helps.