I think a GM's job regarding contracts is to maximize the number of wins per dollar spent, regardless of payroll. I think Jed has been pretty good at that so far.
I think in FA he looks at all the good players they're interested in to inquire on, puts a price value on all of them, and usually signs the guy who comes in at the best price per projected value. If Swanson cost over 200m and Turner came in at less years and money than he did he would have signed Turner. I don't see anything wrong with this, every player has a value and a price, there's lots of good players available every winter to sign so I don't typically see a need to overpay for guys. Even top players are just a number on a page like the rest, it's all a math equation.
He hasn't been perfect at this. He signed Mancini and arguably Smyly over value and we've all complained about it since the day they were signed.
I think there's times he needs to overpay if we have no choice and makes sense from a cost-benefit analysis. He usually buys relievers with the same value-oriented approach, which to an extent is fine, but we went into 2023 with a lack of late-inning relief depth so I think he went too cheap there, and Jed didn't grab us the quality of relievers we clearly needed last trade deadline to get us to the playoffs. I remember Jed mentioning that the cost of relievers at the deadline was too high for them, but an overpay is better than nothing at all and leaving tons of value in the minors while the MLB team flounders a whole season, especially when he's already acquired Candelario.
Re: Trading Cubs prospects for established players, I guess that remains to be seen. Some of these guys will need to be moved because they're starting to pile up in Iowa. Maybe he values good prospects more highly than most GM's compared to an established player with 1-3 years of control left?