Improved Panther offensive production and making the playoffs is a win for Carolina in the trade.
Much better completion percentage, more TDS and less ints for Darnold to bolster his future contract potential.
As with most teams, they usually win more when they perform better defensively. I have been going back and forth with people about the Falcons lately, as the debate has been if they should draft a QB and move on from Ryan. I pointed out that the ATL defense has been poor, their offense has been decent to good (and one year almost record breaking).
In your scenario with Darnold, once again the Panthers will go as far as their defense can take them. Here's the recap from the past 5 years.
2020: 5-11, 350 PF, 402 PA, -52 differential
2019: 5-11, 340 PF, 470 PA, -130 differential
2018: 7-9, 376 PF, 382 PA, -6 differential
2017: 11-5, 363 PF, 327 PA, +36 differential
2016: 6-10, 369 PF, 402 PA, -33 differential
In general, CAR played better last year than in 2019 but did not improve in the win column. They lost 8 one score games. If you buy into things even out over time or those games typically can go either way, then they easily could have had 3-4 more wins last year. So looking just at the numbers, they were close to being a .500 team.
Can Darnold help them close out games? At this point who knows, but his record in one score games with the Jets was 9-12.
IMO, part of the issue for a lot of teams is they make so many changes in a brief timeframe that it is very difficult for anything to take root and develop. For example, Carolina in just a few years . . .
Coaches: Ron Rivera . . . Perry Fewell . . . Matt Rhule
Offensive Coordinators: Mike Shula . . . Norv Turner . . . Scott Turner . . . Joe Brady
Quarterbacks: Cam Newton . . . Kyle Allen . . . Teddy Bridgewater . . . Sam Darnold
Based off of last year, this is a make or break year for Rhule and Brady (another losing season and they most likely will be ousted) and for Darnold (if he shows no improvement it's unlikely any other team would give him a chance to start and he would be cast aside as a backup only moving forward).
So that being said, unless the defense improves, it's unlikely the team will have a better record. In terms of yardage, from 2020 to 2016 the Panthers ranked 21, 19, 10, 19, 19. So even with a fair amount of weapons, they really have been great at racking up yards. In terms of scoring, they ranked 24, 20, 14, 12, 15 (but there can be huge differences in team scoring rankings with just a swing of 1 or 2 points a game).
As I alluded to earlier, Darnold put up a 59.5% completion rate with 213 passing yards, 1.18 TD, and 1.03 INT per game over his career. Bridgewater posted 69.1%, 249 passing yards, 1 TD, and 0.73 INT per game last year. So an improvement for Darnold would be to get to where Bridgewater was last year . . . which no one was happy with and they were quick to move on from him. So Darnold would have to do significantly better than that (or the team would have to win way more) for them to be happy with Darnold.