Haha ok I will not worry myself with the mysteries of magical smoke, as intriguing as it sounds.
I ended up talking to a place in SA (Polyglot's hometown and my birthplace in fact) and the guy was awesome -
took 15 minutes to chat and talk about other photogs who'd bought other transformers, downloaded the Elinchrom
manual and went through it with me, did the maths and agreed that each light would need the 1500W separately.

But in the end I did order two of the 2000W stepdowns so that a. I can be comPLETEly sure it can deal with the load,
and b. when I get around to adding more lights to my kit I'll already have enough plugs for them. If that makes sense.
(Oh, and they were out of stock of the 1500W ones, so just to get on with the show and actually TAKE SOME PHOTOS soon, I
grabbed the best available!) So, happy for now