All sections have sensor arrays and deflectors, but naturally tertiary section has the most powerful ones since they have the main array and deflector dish.
The landing exit is simply a large airlock with a ramp which can extend down to the surface of any planet landed on. It provides a safe and reliable method to enter and leave the ship without having to use the transporters.
The defence cannons are small drop down pulse cannons about three feet long used to defend the ship and the landing exit against invasion and infantry attack. There are 10 each side which drop down out of the hull when activated. Targeting can be set to different parameters, but cannot be set to specifics. That is, one can set it to target anyone without a combadge or with an energy weapon, but not anyone with brown hair for example. The rule is that the sensors must be able to detect it for the cannons to target it. They can also be targeted manually from a central control room two decks above, but one person is required per gun. They provide an easy and efficient way to defend the ship against small targets against which the main phasers would be dangerous or unreliable to use or when power is low. However, they are not infallible since they have limited range, are vulnerable to attack and require some ship power in order to function. When power is down, security teams with phaser rifles are the only option.
The module link manual controls allow manual release of the section the control is in. This can mean manual release from either one or both sections. Should it become necessary to release for example the tertiary module then both the primary and secondary module controls would have to be used. [Note that there is not one single set of clamps for each module but this control gives mechanical and not electronic control over all clamps for the module]
The primary section has the least efficient of the engines of the modules. This is because greater importance is given to the weapons systems. It also contains the largest of the shuttlebays which can be stocked with several combat specific shuttles or star fighters. The placement of the impulse engines gives it greater manoeuvrability which is important for cloaked combat. This is because shields do not function when cloak does and so it is important to be able to strike and dodge quickly when attacking or to be able to jink when being attacked. Also containing the main command crew, it makes the logical choice for single module combat.
The civilians are localised in the secondary section in case of emergency whereby they have the largest engines for escape. The tertiary section obviously has the most powerful engines of the three sections when split due to main engineering being present on that section, but the main nacelles can keep up the speed longer and are the most reliable. Also, the large nacelles are easier targets meaning that in combat it would be easier to disable the warp engines on that module. The secondary section is the most logical choice for single module escape.
Because of the greater power and efficiency of the engines and sensor array as well as the presence of the landing exit and defence cannons, the tertiary unit provides the most logical choice for single module landings. This is because it can better tell what is around and defend itself more easily against attack. Also, leaving the gravitational pull is more easily accomplished due to the greater power of the engines.
Certain rooms take up more than one deck but only have one entrance [e.g. the shuttlebay]. In these cases, the room is listed only on the level with the entrance or interior entrance.