Just my .02 cents.
Tony Elliot shouldn't be the hire. He's worked at a great Clemson program but I think he only even called plays for two seasons, and their offense fell off a cliff once Lawrence left in his second season. Mike Elko is legit and has a lot of great experience, unlike Elliot who has just been with Clemson. Elko has run successful defenses at tough academic schools in the ACC with Wake and at power like Notre Dame, and he's done great at A&M in the SEC with Jimbo Fisher. If you're going to hire a coordinator he's definitely the best option for multiple reasons.
Regarding Garrett, I'm not going to beat it up just because, but if he's hired it has to come with specific guarantees. The guy doesn't have a single second of experience as a college coach which means he's missing the most important role of being a college coach- recruiting. if Garrett is going to be brought in, it can't be under some personal redemption tour where he's running the offense. If he comes in it needs to be as a CEO type of head coach where Duke is making a serious commitment to football by building up a legitimate recruiting department, and where he has a competitive staff budget to hire quality coordinators and position coaches that will recruit, and most importantly, a legit S&C coach since that's the bloodline.
Garrett could work but the margin of error is very small and he will need to be very well supported by the school and athletic department.
Miami just gave Cristobal a 10/80 contract and are giving him a significantly increased staff budget exceeding 8M per year, which surpasses Clemson as the largest staff budget in the ACC. Idk where Duke is but if they want to actually compete they need to get into at least the top half of the ACC on staff budget.