I've rewired 2 old houses using the 'star' approach. On the last one I
split the 2nd floor into 4 zones and used 12 gauge wire (on 20 amp
circuits). One zone was 2 bedrooms, one zone was the other 2 bedrooms,
one was the bathroon (only one but very large), and one zone was all
the stair and hallway lighting and receptacles. I had to use the star
approach because it was all lathe and plaster knob/tube. The knob/tube
removeal leaves a lot of handy holes to run your wire thru but of
course back then there were only 1 or 2 outlets per room.
I created all the runs in one bedroom, brought them to one large
workbox, then ran a line from two bedroom workboxes to a central
workbox, into which I also brought the hot lead. You don't want to
bring any more wires into a box than it can hold and with which you can
work. Five 12 gauge wires require a pretty big wire nut.
Anywho the concept I used (code ?) was to create my runs to the lights
and outlets, bring them to some connvenient 'collection point', then
connect the collection points. One thing to consider, if you're up in
the attic and the attic has usable space, is to do all this below the
level of the floor. This is much more difficult of course, because you
have to drill holes but there will also be a lot of nice, dime-sized
holes already there from the knob and tube.
'Star' can also be used in the basement to do the first floor of a
2-story house, for example), the star being in the basement. If your
basement weren't finished this IMO woul dbe the way to go, from below.
The only thing I don't have an opinion on is the conduit question.
First house I did I had a place I could tack the wires up individually.
Last house I got around the conduit problem by finding a place I could
run a 6 gauge wire to a branch circuit box in the attic. Had an
electrician do that just to make sure it was done correctly, as it
required a new breaker in the main box. Having a branch box in the
attic makes life much easier than running all those 12 (or 14) gauge
wires from the attic to the breaker box in the basement.