Here are two real-world examples of using Rhai:
I've embedded Rhai in Glicol to support sample-level audio synthesis, and the performance is [acceptable]. Real-time audio is very computationally intensive, after all.
I've tried various embedded scripting languages in Rust, but Rhai probably has the best documentation and playground.
For reference, see this survey:
https://www.boringcactus.com/2020/09/16/survey-of-rust-embed...
Recent Koto Lang also looks promising: