Is Ubuntu Touch for phones and tablets meant to be "dockable" with an external keyboard/mouse/monitor? If so, how will the touch gestures for navigation be handled when using a mouse or trackpad? Will applications need to be able to handle migrating across different screen resolutions while running, etc?
The Touch Developer Preview published on 21 February gives a very good and deep impression of the current status of the project. The first focus was clearly put on the set up of kernel and basic services like networking, video, sound and other hardware support. Also important focus was put on the new user interface and the new application handling for qml-based apps.
What you are adressing, the docking feature that allows to establish a PC-like desktop behaviour from the mobile device was clearly anounced by Mark Shuttleworth but not much of that has been yet put into available code.
So up till now it's more a design goal, an idea supported by the fact that:
And this finally makes the first step into the marketing statements before it is actually brought to life by the coding guys.
All this shows that your questions cannot be answered clearly at this point of time. In the Developer Preview we can see new applications in a new user interface. These new applications can also run on a desktop version. Also it is clearly possible to have a conventional Ubuntu running on a mobile device. This project https://wiki.ubuntu.com/Nexus7 shows its feasibility.