I built my game to webgl. It runs at a solid 60fps on low/high end pc on chrome/firefox. I play it on m1 max. It has a frame rate that varies ~120 making the game feel horribly laggy and choppy. Setting Application.targetframerate = 60 does nothing. Is weblg and unity unusable with apple silicon right now?
I tend to give the answer that Apple & WebGL cannot be used together. Did you try profiling? At the very least try building one of the Unity sample (game) projects and see whether they perform well or not. Be sure to use the latest tech stream version when deploying to WebGL since WebGL support seems to be undergoing continuous technical improvements. And be sure to use URP, not legacy rendering.
I jump between a Windows desktop and M1 Macbook, and for smaller projects -- especially game jams -- I'm in the habit now of making a WebGL build and including a desktop build as well. I don't think I've ever gotten a Unity-WebGL game to work on my M1 machine while my desktop with an old graphics card can run them fine.