In the 1980s, with the development of MIRVs you had a much more efficient way of causing wide area of destruction. Assuming you wanted to hit Moscow, using 5x200kt weapons would be much more effective than one 1mt weapon. Particularly large warheads would only be useful for deep/hardened targets. You don't need to knock down every structure in Moscow or NYC to "destroy" the city. You will get huge firestorms which are quite effective - look at Dresden which was not built of wood/paper like Japanese cities - and these will kill lots of people and destroy structures that were not trashed by the blast waves. If any of the blasts were ground bursts, which means the fireball touches the ground even if exploded above the surface, you now have significant long lasting radioactive contamination and fallout spread in the vicinity. This combination will render a large chunk of the urban area "destroyed and this is one missile, one MIRV. Targeting using nukes is a somewhat straightforward engineering problem, although being creative to achieve the damage required with the least resources is a bit of an art.
In terms of boomers, it depends a good bit on how the war starts. The "other side" surging boomers will be an indicator. In any case in the 1980s the USA/NATO had a pretty good at tracking Soviet SSBNs outside of their bastions. OTOH the Soviets rarely if ever in the 80s were able to find our boomers (not sure about the French and British). In terms of bombers, since they will be coming in after the missiles have hit, both sides will have difficulties with their air defense systems.
Bottom line you first define the damage you want done to a given target, and then solutions are worked for various systems. Factors included are the probability the system will work (missile launch, aircraft not abort etc), the odds it will reach the target area, the CEP of that system, etc. Of course, nukes that miss the intended target but still land somewhere and go off will add to a more generalized destruction and more widespread fallout.