I don’t have much technical expertise on war plans, but I know about NK air war considerations.
North Korea has elements of the old Soviet IADS – the network of radars and anti-air missile sites designed back in the glory days. Many such missile systems have limited range. However, some have incredible range, more than enough to cover the entire Korean peninsula and beyond. These systems, although meant to take out aircraft, involve space rocket-ship sized missiles to achieve that range. This means they’re expensive, and I’d bet there aren’t as many parts lying around anymore. If you check Jane’s, you might find that NK only would have a relatively limited number of these systems.
A B-2 bomber – along with all of the Air Force for now – was a Cold War strategic asset. Part of the doomsday machine. That’s why its huge expense and the fact that maintainers were poisoned to death by its special stealth paint is “no big deal”. It’s a desperate measures machine.
Since the 1990s, the Air Force has been converting its desperate measures machines into run-of-the-mill workhorses. Some retired officers have complained that these expensive machines are overworked, for mundane Afghanistan bombing missions whose need was way below the planes’ intended purpose.
The B-2 has stealth, which is a capability that doesn’t exist in any other major bombing platform (that we know of). So, it’s the “when you absolutely positively have to kill something deep behind enemy lines” plane. Those few long-range missile systems seem like a good candidate, and bringing B2’s in almost certainly has to do with that.
Without the long range systems, NK can’t prevent general access to the rest of the air fleet into their airspace. So it could be a free for all.
Even if the objective is “just” a bloody nose special forces take down or even long range air strike from a cruise missile, you’d have to take out the long-range missile threat, and probably also make space for other assets to suppress or deter any other shenanigans NK might want to try (like an attack South).
As for the B-52s, the point there is that they can carry a lot. One day they might work out a way for Cargo planes to carry cruise missiles into the air doctrine, but for now only the B-52 can carry a meaningful payload of long range strike packages.
So, what you might have is 1) take out the long range missiles with the B-2s, then 2) fly in to medium range with the B-52s to launch cruise missiles at NK nuke sites. It could be that limited and “clean”. And the deployment of air assets could be little more than a posture. Remember, officers get pay and performance bullets for even inconsequential little ballets. Some major needs to write that he coordinated the deployment of B-2s to Guam, so he can be a colonel some day. The bureaucracy loves excuses to do this sort of thing.
On the other hand, the deliberate choice to use a tactical nuke in this situation would be an explicit re-framing of American doctrine. If the Pentagon – with their paranoid perspective and powerlust – is worried about the problem of small states proliferating nuke technology to hedge against American hegemony, then they might see the need for a heavy hand.
The doctrine is: obtain nukes, and get nuked whether you use them or not. A notion of proportionality well suited to a bully.