Peugeot 406 2.0 auto LX

This is the first Auto I have had so sorry for the questions if they
appear silly.

On the dash you have the what gear display
When the S on the gear box is pressed the S on the dash does not light
is this normal.

If the above is normal How do you know what mode the gearbox is in ?
(S or not)

Car seems to stay between 2000-3000 most of the time.(which hopefully
will keep fuel cost down a little).

Should the 2.0 auto be pretty handy at pulling away I seem to be
having probs pulling away from traffic lights car seems to stay in the
low gear to allow revs to get up and then when it chages gear revs die
and so does car Acceleration.(Annoying drivers behind I am sure).But
on short burst it seems Ok across a junction.

Whats the best way you have found to drive using 1,2,3 or just leave
in Drive ? Anyone have any prefs and reason why.