It is about the three ship classes. Constitution, Miranda, and Constelation Class. What are the different? Why making three different Ship Class if they are basically the same?
Because in Star Trek II, the Reliant needed to be a different style of ship, so that when she was in battle with the Enterprise, you could easily see which ship was which. The Reliant was originally going to be the same class as the Enterprise until they realized that that wouldn't work for the above scenario.
For the Stargazer, it simply came about because someone got the idea that the yellow kitbashed desktop model built for background decoration in Picard's ready room was actually his former command. They were going to use the TMP Enterprise for the Stargazer as well, but Greg Jein ended up building a studio model based on that desktop model.
For Constelation Class, why would they put 4 warp nescele (or whatever it is) when the performance not even better than the 2 warp Nes... errr Engine starship like Constitution.
How do you know the performance isn't better?