Don't think Smart would have made a bit of a difference. IMO, he is a good HC, but one of the more overrated coaches in the country. He has no imagination, what is he going to do now that CNS is gone? Can't ape his adaptations or take advantage of CNS' player or assistant evaluations. (In fact, he's stuck with TRob now - he, he. Mike Bobo - sounds like a late-career CNS hire.) Kirby is as focused and ruthless as Saban, but that's where the comparison ends, IMO. He's gotten a good head start, but his free ride in terms of SEC schedule is now over.
Assuming CKD and staff can figure out a way to stop UGA's power running game, assuming that Bobo/Smart have enough sense to use it, CKD will out-coach CKS probably every time they play. UGA may win, but it will be because of overwhelming talent.
I can't believe the number of fans and analysts who have such high regard for Smart. He's a good coach, but hardly elite. The primary reason for his success is that he trips over 4 HS AAs when he walks out of his back door every morning. If your team can complete the forward pass and get a few stops, he's in trouble.
And Sarkisian is a very good OC, but just a meh HC - his first 8 years 7,6,6,6,4,4,7,5 losses. Then this year. But he will do well with Saban's old staff and the trillions he has at his disposal now that money means more than ever. CKD beat him in each of the last 2 years with less than half of the raw talent.