On the first question, it all depends on what action you are animating. For example: If the character is doing an roundhouse kick. Yes you can use IK to do this, but it is easier to use FK. Why, you might ask? keeping the knee bent while raising it to hip level can be tricky with IK. Also getting the knee to point in the proper direction using IK is easier, but the movement as a whole is easier with FK.
For your second question, it depends on if the rig’s options and is more of a preference thing. There are case where one is preferred over the other, but mostly it’s a mater of preference. I don’t know if it’s because of the similarity of our name 🙂 , but I also prefer the Pole Target vs the leg twist.
Yes, the arms have an elbow pole target/twist.
