Yes the impact drivers can do the work of a cordless drill.

Here is a decent article on the differences between cordless and impact.

On a different note, I have typically found Ryobi to not be as well made as other name brands. The quality difference is usually reflected in the cheaper Ryobi price. If you do not need the reliability and will use the tool occasionally as a homeowner, Ryobi is a good value. Just don't expect it to be able to do continuous heavy work.