Watts are not light output.

OK. So how can I figure out the answer? Do I try to find out the lumens?

If I look up "13 Watt GU24 Base CFL Light Bulb" I can find one for sale that has an output of 950 lumens

I can find a 32 watt T-9 circline bulb with an output of 1950 lumens and a 22-watt t9 circline bulb with 675 lumens.

So,

Is the answer to my question now:
4x950 = 3800 lumens
vs
1950 lumens + 675 lumens = 2625?

Or do bulbs of the same size vary in light output?

Lumens would be a better measure, but even that can be affected by fixture design.