From what I could work out about the Gene Simmons demos, the recording started in LA with VH's gear including the car horns on RWTD and it's mostly just some solo bits that were overdubbed and the mixing that were done in NY.
EVH was using the variac at that time (late 1976) and I think he was using the Ibanez Destrroyer as well (there is the telltale Ibanez Destroyer harp like sound at the start of Gene's RWTD) but there is no Strat on them because EVH started using the Strat after the Gene Simmons demos were done, it's all in the VH boots btw.
Hardly anyone points to the Gene Simmons demos and shouts Tooooooooooooooonnnnnnnnnnnneeeeee!!!!!!!!!!!
The recording studios in LA and NY are different to Sunset Sound and Genes production is basic, but it was only meant as a demo of VH.
Then Ted Templeman does the Warner Bros demos with VH (around mid 1977) and they are good but not polished and then the recording of the first album starts on August 29th 1977 at Sunset Sound.