Most players will use a backhand grip as their starting defense and switch the forehand only if the shuttle gets hit deep into their foreahand side. I even as times still play a net shot from this angle with a backhand grip lol
when I play, if the other partner (doubles) in closer to the net I will generally switch to a forehand and drive it to the opposite corner and then follow it in for the short return. Works almost all the time for me. Just keep in mind when you're cheating in to remember the skill of the opponent. If they are strong dont cheat in as much for the straight cause they could you a cross.
Yes you should ready backhand grip for cross court smash. If you are on the left (assuming you are a right handed) the bird should land on your left. And if you are on the right, your return can counter attack the left side of your opponent. So both sides, yes backhand grip smash return is the best option.