Rc's yo, the kind that curcumvent the law. They're all kind of lab made, otherwise they'd be extracts, which are more like... a traditional shamanic and or indigenous kind of thing. Like peyote and zoomers etc.
Generally speaking, chemicals conceived in a lab are all, for all intents and purposes, research chems at some point in their life cycle.
But I'd imagine in this context, RC's would be molecules analogous to existing, scheduled recreational (outlawed) drugs that already exist.
Like; 4-ACO-DMT, or 1P-LSD, 3-MEO-PCP etc.