3) The Sovereign was created during a time of crisis and potential war for the Federation while the Galaxy was created during a time of relative peace.
The Galaxy class was designed during the Cardassian Wars.
The Sovereign class would probably have been designed in the early 2360s. Thinking about it, this is more likely to be described as a time of relative peace than the above.
I don't think that metric makes much sense, though. All frontline starships are capable of defending the Federation. I don't believe they intentionally reduce the capacity of new designs to carry out that mission just because there is not a huge war planned or ongoing at that moment. The top-of-the-line designs are as powerful in this respect as they know how to make them.