Shut panels off first? Or controller to batteries?

Generally panels to controller first; some controllers will die if they have input but nowhere to put the output power. Others may not care one way or the other.

It's never unsafe to do the panels first, since the controller has to deal with nighttime where there's (essentially) no power from the panels but the battery is still connected. In other words, it's an expected situation that the controller needs to be able to deal with, whereas the opposite way around is not generally expected.