You can use either, but a DVD-ROM will give you much more flexibility by letting you rip both CDs and DVDs. The LiteOn 166 is an excellent choice, it has excellent DAE speeds for CD ripping as well as 16X DVD ripping speeds.
Depends on the actual drive and not whether it's a CD or DVD ROM. The LiteOn 166 is plenty fast for any ripping you want to do - it's the one I use for all my CD and DVD ripping chores. I'm sure there are others, but the 166 is the only one I have personal experience with.