I've used various Syngonium cultivars over the years, never had a problem with toxicity. Syngonium is another one of those 'can't kill' plants like the close relative, Pothos, that we use. I prefer to use Pothos because it doesn't take over quite as fast as Syngonium and is a wee bit sturdier for jumping geckos. However, either one will thrive on neglect and a bit of moisture, so they're foolproof. Syngonium should do well with the smaller Rhacs, though I don't know for sure how it would stand up with Chewies. It's a no-brainer that it won't work with leachies.