I think you should able to hire coach or fire coach even you turn off the owner mode. All you have to do is keep checking the NFL news to see any coach whom you want, been fired recently by the computer, and then go to coach option and select him.
It depends on who you are talking to or your styles of your offense. If you like to pass a lot, I would recommend Raiders play book, and if you want to balance your offense which I highly recommend you, I use the Packers, or west coast offense. If you want to run, I think EA also has a play book which are heavily desired for running plays.