Thus far the Tommy Rees offense has only had Ian Book as the QB. Ian is mobile, accurate and doesn't make mistakes, but (probably due to his height) didn't see the field well from the pocket and therefore missed a lot of guys, he also didn't have the biggest arm, which prevented a lot of downfield throws.
Coan is tall and accurate, but not a scrambler and doesn't have the biggest arm. But Coan sees the field well, so I expect a lot more mid-range completions over the middle.
Angeli seems like Coan as far as his skillset. Maybe not quite as tall, but with a slightly bigger arm. I think an offense tailored for Coan will also suit Angeli's skillset. We'll see this year if such an offense can be effective or not. I think that it is telling that the 2 QBs that have committed to ND since Rees took over as OC are Coan and Angeli.