Google Chrome is already optimized for Apple Silicon. When will Mozilla Firefox be optimized for Apple Silicon? Will the download process look something like this? 
I think the latest Firefox beta supports Apple Silicon, but is it a Universal 2 program, unlike Chrome? When will the stable version of Firefox support Apple Silicon?
Yes, FF Beta is a universal app. You can sort of follow along with development but I don’t know how what’s over there translates to the beta being deemed ready for production. It’s a good sign that it’s into beta from nightly already, though. https://bugzilla.mozilla.org/buglist.cgi?quicksearch=apple+silicon
(If you’re seeing nightly or beta still showing as Intel, just manually replace the app instead of relying on the updater. It seems like a lot of programs are like this.)
That is awesome! It frustrates me that Google Chrome isn’t a Universal 2 program. Does Mozilla Firefox also have a new icon to fit in with macOS Big Sur?
I can’t tell if it’s sized right for Big Sur or not.
On Catalina:

On Big Sur:
It still looks out of place. 