Elite Ships vs. Swarms

Most games require a few elite ships and lots of smaller ones. Units to
look for are command ships which allow bigger squadron size. For example: A
battlecruiser with a CR 6 AS 8 AF 3 vs. one with CR 9 AS 5 AF 2. The first is a
nice warship but if I have good escorts I can pack more AS and AF into the
squadron with the second ship. If I have a frigate with a CC 1 AS 3 AF 2 I can
put 6 in the first squadron for a total of AS 26 AF 15. The second ship can
hold 9 frigates for AS 32 AF 20.

Line Formation vs. Divided Task Forces (when using Starmada / Tactical
Resolution)

Not sure exactly what you are asking.

Multi-Purpose vs. Specialized ship designs

Most ships will either specialize in AS or AF, very few are multi-purpose.
The high AF ships can guard command squadrons where enemy fighters will probably
be targeted. Other squadrons want higher AS ships since the command squadron
halves AS value for the higher formation bonus. The exception is ballistic
ships which maintain their AS value in command squadrons for a higher
maintenance bracket.

Concentration of Force vs. Distribution of Force (i.e. concentrate your fleet
for one decisive battle or fight many small ones)

This one depends on the warp line layout. If you have 1-3 choke points you
concentrate. If you have more contact points you spread out and try to have
superiority when you fight.

Strategic Centralization vs. Strategic Decentralization (mainly how you treat
and use your fleets - are they self-sufficient or do they rely on being part of
a larger system?)

Supply ships are costly in terms of maintenance and of limited use.
Keeping in supply range is a must unless you locate a shipyard, etc. and can
make a deep strike on infrastructure.

I'd be very interested to know where other VBAM players see the advantages and
disadvantages of each axis and where they would see an optimal strategy.

I like carriers, being aggressive and switching the axis of attack to keep
my opponents off balance. The new version won't be as bad but maintenance
groups were king for me. If I kept full maintenance groups I could save 1-3 EP
each turn in maintenance costs which gives you 4-8 more ships each year. With
the new fractional accounting coming up you won't have this.

The other thing to really consider is AS and AF value vs. CC. If the
destroyer is AS 5 AF 2 CC 2 and the frigate is AS 3 AF 1 CC 1 you want 2
frigates not one destroyer most of the time. A CC 3 cruiser that is AS 8 AF 2
also doesn't add up if it isn't in command. Don't discount smaller carriers in
battle squadrons as they increase fighter coverage. For command squadrons try
to put either a ballistic ship or a carrier with low AS in command.