well I already bought the cinestill since it was touted as being the same film just reappropriated for stills, at this point I'm just confused as to why it's rated at 800 if it's supposedly a 500 speed film and how should I expose it? Should I just assume it's virtually identical to 7219 and rate it at 500? If I do that, should I tell the lab to process it as 500?
It's not the same. If it says 800T, the manufacturer has set the index exposure (IE) to be exactly that. Those are two different ASAs with a 2/3 of a stop difference. You need to pick one. I would probably rate the CineStill at 400 (since that is closer to the ASA you will be working with) and tell the lab to pull process the film 1 stop.
Apparently, Kodak 5219 is the source material that CineStill is based on. But that's it. CineStill has an ASA of 800T, whereas Kodak's 5219/7219 has an ASA of 500T.