Hello, amdgpu is the default driver and is the best for gaming as of right know. It’s included in most distribution. No need to worry.
There are programs to do so but the best way is to keep steam running in desktop mode and change the controller mode into steam as per the Wiki
To call the virtual button is steam + B on steam deck, so it’s the big button on the right + B for us. But you need to have enabled handheld daemon. Did you enabled HDD at boot?