I’m just a random internet stranger and claim no authority on the matter, but I think almost any dual 240 setup would handle any cpu/ single GPU combo. Granted, it might not be as easy to cool as a more modest setup, but still not a big hurdle.
As for a cpu and two gpus..... idk but would depend on the hardware.
The thermal load of the specific components are going to play a pretty large role in determining how much dissipation you are going to need, but like loader said, 2X 240s should be able to handle it. One thing to consider though is how much pressure head you're going to need for 2 rads, 2 GPUs and the CPU block. Make sure you get a pump powerful enough that you don't end up with fluid stagnation.