Ok, I did some rough math. The W88 has a diameter of 55cm, a length of 175cm, and a blast yield of 475 kilotons. The unpressurized cargo hold of the Starship per Wikipedia is 88m^3, and the diameter of the vehicle is 9m. Let's assume that the unpressurized cargo hold is a cylinder 9m in diameter with a length of 9m.

It looks like a hold of that size could fit 15 units per 200cm length, or 60 units, with space for structural rails and deployment gear. For comparison, that's 7.5x the capacity of the Trident II SLBM which was designed to accommodate 8 W88s.

In terms of potential, one W88 detonated in an airburst would produce a fireball over 1.56 sq km, an air blast to 5psi overpressure over 91.9 sq km, and 3rd degree burns over 233 sq km.

The scale of the human tragedy involved in a first-strike deployment of 60 of these things is too gruesome to write down here, but you can play with it on NukeMap [1] if you're so inclined. Suffice it to say that no sane government on the planet will want Starship to land anywhere nearby unless we're living in a global utopia where this sort of thing is unthinkable.

[1] https://nuclearsecrecy.com/nukemap/