I've been a bit of a one-note-Johnny on the subject of leaving the brood nest alone.
Would be useful to clarify and expand on the limits to disturbance.
I don't think lifting the cover and peeking "under the hood" has much material effect on the hive. In a hive with honey supers, you frequently can do that without smoke, and with no apparent alarm reaction from the bees tending the curing nectar. In a single story hive or nuc, just observing the "cover" of bees on the top bars- tells you loads about the condition of the hive.
Smoking changes the bee behavior-- I'm not sure how long the residual smoke disrupts the hive, on light smoking I don't see any fanning to remove the smoke. A old beek whom I befriended described deliberately smoking hive to encourage wax production. The idea was wax is generated by house bees with their crops filled and no place to put the syrup. Smoking makes bees fill their crops>hence the idea this artificially encouraged wax (and comb drawing).
The critical question on a new hive is there brood and eggs, and what is the pattern. This can be observed by 1) looking at the cover on the top bars, and 2) moving in from the side until the first frame with brood is observed (typically on the outside of the #3 frame). This is often just a softball (or smaller) sized pattern on the exact center of the frame. These are typically among the youngest brood- so are the most recent snapshot of the queen activity. There is no need to go any further. Stop there.
I don't see hives swarm without raising a frame of drones, if you got to the outer edge of the brood cluster without seeing a frame of drone brood below the pollen archway on #2 -- the hive is not swarm ready. Queen cups may be further inside the nest -- but these are an internal matter of the colony for supersedure-- if you see eggs and brood, you don't need to make any intervention.
In declining hives with chalk brood or simply a failing queen, the outer brood frame is usually the most afflicted and the dead abandoned rather than cleaned awsy (the declining population pulls toward the center of the nest). So you are most likely to detect these problems on the outer frame.
In my observation, while honey frames are often only drawn from one side, the brood frames are usually matched front to back with larvae. This means the outside of the frame carries some brood before the queen and consorts move onto another frame.
A hive without brood won't cover the top bars in the same way, no brood to cover so the nest disperses more widely.