Choosing correct relay for LED power supply rating
It depends on which side you are switching. 

If you're switching the secondary then you got it right.


  A = (4 * 96W) / 24V = 16


Choosing a 16 A relay here is fine but it might be a good idea to choose a higher rating to be on the safe side.

If you are switching the mains voltage, I suggest the following:

Looking at the information given we can see that the power supply has an efficiency of 82% and a maximum power output of 500W. With this information we can calculate the maximum power input by taking:

500 W / 0.82 = ~610 W

With this information we can now calculate the current on the primary side:

610 W / 120 VAC = ~5,1 A

So a relay rated for atleast 5 A would be enough in your case since you won't be using the full 500W.

Be careful if you choose to control the primary side!