> Would each city be targeted with one warhead, or blanketed with several over a large area?
It depends on your objective if you want to incinerate a target, maximize damage or produce maximum fallout.
Basically if you want to incinerate a small, hardened underground target you need to send a few nukes to have a high confidence level of success. If you want to damage a city and are OK with detonating in any part of the city then one might suffice. If you want fallout then you want an air burst to the West and let the Easterly winds spread the fallout.
Each missile has it’s own distance and accuracy calculations.
The author has another site called Missle Map that explores these scenarios in much more detail: