[Nonfractal]

Top down, 
It's  a master's thesis to write up slot car body/pod setups and how they affect handling. 

The only consensus I hear is that no one (in magless racing) locks the pod up solid.
In every other aspect, you will find a huge range of opinions.

The pod setup insulates the chassis from the motor's torque and the motor from the chassis vibration as it corners and traverses track imperfections.
The pod acts as a Newton's cradle transferring momentum from one component into another.

The best 3 word description I've heard is "Primitive mass damper" (Gary Skipp) 

Certainly , different pod config (angle winder , side winder and inline) seem to require different tensions and different amounts of play. 

Pods can have 3, 4, 5 or 6  mount point depending on the manufacturer. 
Pods are available in different materials and thicknesses which affect the cars handling.

Suspension allows some control over the weight transfer under cornering and acceleration/braking. 
On extremely rough tracks, suspension helps keep the car on the track. In very extreme circumstances, A suspension guide can also be used. 

Suspension allows control over the torque forces produced by the motor. 
Tuning the suspension screws can allow you to mitigate against too much or too little traction at the rear.
Selecting different springs can help mitigate against bad car behaviour, such as start-line power DeSlot (without loading your car up with ballast)

I would say that the more torque the motor produces, the more important the suspension becomes.
BSCRA racers will be laughing all of the way through this write up. BSCRA have No suspension pods, massively powerful motors.

So, how to learn how to set up pods? 
Left and right springs should be identical and under identical tension. 
Front to rear, tensions and springs can be different and create good car behaviours.

Take one of your cars that has a bad behaviour and experiment. 
Or take a car you are happy with, alter the pod setup and observe the result on track. 
You'll see top racers often have a screwdriver to hand when testing and tuning a car at a club.

Once you get to grips with pod setup, you'll be able to alter the car's handling by very small adjustments and be confident that you can predict the results of each turn of each screw. You'll also be able to create a suspension type behaviour where a class of racing prohibits springs.

AlanW