Trump allegedly discussed US nuclear subs with foreign national after leaving White House:...

Discussing known information isn't an issue. Discussing patrol packages would be.
The most sensitive pieces of information are the patrol packages and the metallurgy and blade build on a boat. Reactor stuff is sensitive too, but Jane's has the specifications for every piece of military hardware. I've often thought that they have too much information.
The number of warheads that are on a missile rarely ever are the maximum number that it will hold. START II limited that, and it can't be changed underway. Trump wouldn't necessarily know how many warheads would be attached at any given time unless he asked for an inventory, so bragging about capabilities when he's never been on a boat is more about braggadocio than actual knowledge.

That said, I still think he's not the brightest bulb in the pack but he's head and shoulders a better leader than Biden will ever be.