It's not that we don't want to answer but we are busy too and some things are easier for you to find than for us to answer.
IMO the order of finding information is that:
1. Check the documentation and/or older forum posts
2. Check the code
3. If still don't understand, post in forum
Answers:
1. Both controls are good for that, depend on your context one may fit better than other.
2. Same as 1.
3. PopUpTable inherit from ArrayCtrl so what you can do with ArrayCtrl you can do with it too. DropGrid inherit from GridCtrl.
IMO GridCtrl provide a higher-level interface when ArrayCtrl is more low-level.
The best answer only you may write after testing them in practice.