I've been using Firefox mobile since they enabled extensions on it a little over a year ago on my Pixel 9 and haven't had any performance issues with it. My only complaint is that it doesn't handle form auto fills, or opening links associated with apps as well as chrome, but I think that's because of chrome's inherent ties into the OS. I prefer Opera on desktop for the UI and features.
I've been using Firefox mobile since they enabled extensions on it a little over a year ago on my Pixel 9 and haven't had any performance issues with it. My only complaint is that it doesn't handle form auto fills, or opening links associated with apps as well as chrome, but I think that's because of chrome's inherent ties into the OS. I prefer Opera on desktop for the UI and features.