general principle of autocad question

Hi,
Totally new to CAD progs.
Is it that when starting a drawing of an aircraft, one has to decide from
the outset if its to be in 2D ortho view, front, side, plan underside etc
views as first or third angle projection, or if its to be constructed
instead as 3D objects ?
If as 2D , will a canopy drawn in plan view and side view be generated bu
the prog in front view, rear view and as a pecked line in underside view ?
If not, and the user has to do traditional projecting of lines, hitting 45
degree to cast down to the front view from the plan view etc, traditional
draughting in effect, and errors creep in, would wanting to create a 3D
model from this later on be full of problems ?

If on the other hand one starts out creating 3D objects that in time make up
the aircraft, this would I assume generate 2D ortho plans for use in
aviation books etc. for scale modellers.

The trouble is, if I have but a few WW2 plans, some site measurements with
ruler and curve gauge of the item, a stack of pics, some plans of
individual airframe components etc, which need a certain amount of detective
work and positioning, tracing over etc, to bring this jigsaw together, would
the 3D approach be feasible. I so far have drawn 2D plans from such, but
seek the ability to see a prog generate items in the views I havent drawn it
in. Many site dimensions are taken over the aircraft skin, sometimes
following a known internal frame, sometimes diagonal following just skin !,
usually the former way. Can these be plotted in autocad and how ?

Hope this makes sense as a question.

Steve