It’s under the shield on the left of the address bar, better protection against tracking enables this and a bunch of other features. Also on by default in private mode.
Now, if you want. There will probably always be tradeoffs between the two drivers so I doubt this will ever match Nvidia’s across the board, just have to pick your poisons.
I haven’t used it because most games don’t work or have as good of performance. Benefits in short term will be things like in-tree kernel module, better working relationship and bug fixes with open projects like KDE/Gnome and maybe things like Gamescope or VR.