To start, even lighting is critical. That often means having a larger studio space than you might expect. You need separation from the green sides/background to minimize sill onto foreground matter.

<sigh> I'm old, I guess. When I started my career, I was involved in the production of hundreds of commercials where the CEO of a supermarket was composited over extreme close up beauty shots of products. Back then, around 1990, there was only one acceptable way to perform blue/green screen; Ultimatte.

Proper compositing has tools to remove spill edges and reflection from objects. With care, you can composite ice, smoke and a glass of water...with no green in the final result.

Today's most common software tools do not have such depth of features. Most especially those that work in real-time. They're great at compositing the weather guy against the map, but no so great at complex composites.

I wish that there was some kind of plugin that allowed more complex compositing in vMix.

If you look around you may be able to find old demo reels from Ultimatte, who is now part of BlackMagic Design. In the hands of a master, they could key smoke, fine hair, flowing water, glass. It was really amazing to use.