Gweilo: A Cantonese term tossed about in Hong Kong which means - depending on tone or level of inebriation - White Goblin, or Devil, or Foreign Ghost. It’s always applied to white people, and it’s never complementary.
Renminbi (RMB): Is the official name of China’s currency system, similar to the way that the Sterling refers to the British currency system. It means “People’s Currency”, because of course it does. The yuan is a unit of that currency, like the pound in Britain.
Essentially, use Renminbi (RMB) in high-blown formal context like: “The Renminbi is gaining international recognition central bankers attempting to kowtow to Beijing.”
Yuan is a unit of account: “What can I do to get you into this EV? It’s a steal at 225,000 yuan!”