“Everyone does” have nuclear weapons, where “everyone” includes more than one independent sovereignty, is not a long-term equilibrium state, it is a metastable state, prone to rapid devolution to “no one does”, possibly with a side order if “there is no one to”.
I am responding to you, and disagreeing with your claim that the first of your options is a viable long-term equilibrium, contending that that is only true under the degenerate condition of a single sovereignty, otherwise it is a metastable state [0], not a stable long-term equilibrium.
I prefer later. As nuclear weapons are the great equalizer. A country with larger conventional army won't be able to bully smaller one... And you really need that sort of capability for equilibrium.