To the OP, it's the summertime so expect fans of all fanbases to pretty much gloss over weaknesses and over-hype strengths. The only real exception are the fanbases that have turned on their coaching staffs.
Anyways, 1) UNC had success last year because they mostly forced us to have long drawn out drives that ended poorly for us. We had the following drives
8 plays - 69 yards - FG
10 plays - 61 yards - missed FG
12 plays 50 yards - FG
10 plays - 62 yards - fumble
11 plays - 57 yards - turnover on downs.
That is a total of 51 plays and 299 yards to get 6 points. We death marched ourselves to death. Finish those drives and we win or are much closer. There was a similar issue against Kentucky which is why the game was still one score late in the fourth despite us overall playing much better, but fortunately we had a defensive TD, a punt block setting up a short field, and the defense pretty much stuffed kentucky until the fourth quarter.
2) It was less that UNC had a plan to copy, and more with our own stuff that game. IMO we'll see more of that style next year between a new QB, the loss of Marshall along with Mills' running style, and the tendency for Jordan to call his own number. We'll likely see several games like the UNC one in terms of several long drives. Whether they can be converted to 7 or not is the real issue.
3) The reasons for optimism are we have experience returning on the OL and at the skill positions which should lead to fairly consistent blocking. There's also a good chance that our D will take a step forward. We also have some pretty good recruits coming in at the positions of need, specifically the punter and place kicker. I still think it's a bit silly to expect to be better. Losing Thomas is absolutely killer, more so than people are acting like, and the loss of Marshall is also being overlooked. Also, while we have some good recruits, you have to expect some dropoff with the losses of Butker and Rodwell. Also, while I believe the defense should continue to improve, we do lose a good bit of the front 7. Unfortunately with the way other teams are shaping up I feel that we'll run into more teams testing us in the middle rather than our secondary, which is our strength. IMO this year will feature growing pains for both the offense and special teams, and the defense won't make enough of a stride to prevent a bit of a regression. IMO 6-8 wins is a reasonable expectation this year, and I think 2018, and maybe 2019 depending on QB situation, are more likely to be our next "peaks".