its my understanding that FASI works best in dlimo and FASA works best in xylene
can anyone offer supporting evidence.

do either FASI/FASA have a tendency to salt out only mescaline or do they both salt all alkaloids that would normally be retrieved via acidic water solutions (hcl and acetic)

Infundibulum once tested adding FASA to limonene and it formed two distinct layers instead of mixing and precipitating the alkaloids. I seem to remember adding FASA with a small amount of limonene and the alkaloids precipitating, but I can't remember for sure. Try FASA out with small amount of limonene with alkaloids and let us know.

As for whether there are different cactus-alkaloids in the different types of cactus extractions, this is still a work to be done AFAIK. TLC would already be a great start.

I did FASA precip from d-limonene with mimosa alkaloids recently. The limo and the FASA mixed well, no separate layers. I started by adding just a few drops every minute or so. The clouding didn't sink at all, so i started adding larger gulps, and the FASA thinned the limo enough for (most of) the precipitate to sink to the bottom. I recovered the ultra-fine floating fumarate in a coffee filter, and scraped the crystals from the bottom.

(Edit: The light in the right half of the precipitating pic is not UV, it's just colored LED to make the cloud more visible)