Emulation apps in iOS 14.2 receive Just In Time (JIT) compilation, meaning they can run at full speed.
However, that doesn’t mean you’ll see emulation apps in the App Store, or even any other app using JIT. Testut told us that the current implementation works only for sideloaded apps, which are usually installed through Xcode and other developer tools instead of the App Store. In other words, this is a feature intended for developers with debugging purposes.
Check It Out: Emulation Apps Get JIT Compilation With iOS 14.2
The internet archive’s internet arcade emulation boots in iOS but doesn’t seem to support controls properly yet.
With webasm support in Safari as well as canvas/webgl/audio/controller/touch support in webkit, there’s no reason emulator apps shouldn’t run well as web apps.
Consider that Amazon’s Luna is running as a web app – emulators for older systems are likely to run well, and with low lag given that they are rendered locally.