Their small selection is already insanely helpful for me. I've been using firefox mobile for a year now and it's just as fast as chrome with the additional benefits of:
darkmode
adblocking (including youtube!)
shorter, more sharable links without tracking
and thats all thanks to the extensions that arent available in other mobile browsers unless devs directly integrate them into your app.
Don't forget the "Video Background Play Fix" add on. That paired with the adblocking makes it where you can watch ad free YouTube while in another app or even with the screen off.
The only thing that isn't quite on par (for me?) is 60fps videos. Those only play on 30. The 60 option isn't available. Maybe that's a codec incompatibility?
Nah, I did the following:
I picked a video in my Youtube app that I know has 60fps options. Then I switched to Firefox, played the same video and checked the quality options.
In the app, it gives you the options 720p60, 1080p60 for example. In firefox, it does not.
Here's another trick. Go to youtube and then go to your Firefox menu and check "desktop site". And then you can install it as a PWA on your Homescreen. Don't worry, when you open it up for the first time from your Homescreen, it will be back in Mobile web format.
This essentially makes it an isolated app from your browser. Not cluttering up your history and tabs.
I replaced the YouTube app on my SO's phone with a Brave Browser YouTube link (Brave includes both features out of the box) because having to sit through ads when they wanted to show me a video was driving me nuts...
I use Firefox because of tamper monkey, buy Brave is my go to easy solution for friends so I don't have to explain about installing extras.