Hermes itself is already faster than JSC, which is on par with V8. This just puts it way ahead and probably closer to Swift/Kotlin code, at least in the realm of mobile apps.
We've seen the opposite for networking related activities especially when there are 100's of requests that can happen on certain screens. We've tried using Hermes but didn't see any differences other than the app bundle increasing in size.
From what I've seen Kotlin(and Swift prob also) semantics are fare more AOT-compile friendly so they're probably a fair bit ahead (depending on how much you gimp your JS target to mimic Asm.JS/Wasm but most regular JS developers won't write code that way).