The games are live but its not just the Bills, its other games too. To me "cast" and "mirror" are the same thing and to be honest I don't know, have never tried it.
If we are playing at the same time as say the Jets, sometimes I put their game on my phone if it is a close match. I suppose it will depend on where one lives... I'm in Florida so nowhere near to back home.
No sir, I've had a choice between 6-7 different games on the app.