The differences between the NX-01 and the NX-02 are a Deflector dish and the colour of the hull.Like how the NX-02 looks a little different to the NX-01.

The differences between the New Jersey and the Enterprise are far more significant. The shape of the upper saucer is entirely different, the windows are entirely different, and the secondary hull has some minor differences. Which I'm fine with.
I'm just saying it's odd to go to the trouble and use the resources required to build an entirely new model, when they could have simply used an existing model and achieved the same effect. The Constitution model used in season 4 of Enterprise was far and away a better looking rendering of a Constitution. The one seen in Picard was just ugly by comparison.