CX power supplies are good for budget builds that run well under 80% load on the supply. Also good for replacing OEM supplies. While Corsair does show they can do continuous output at their rated wattage, they are not intended to do that for long periods. They are to be avoided on setups that can overclock and support multiple GPUs which will have load spikes that will exceed the capabilities of the supply.
Better built supplies are rated for continuous output at quite warm temperatures. Their short term output capabilities can be staggering. Better stability as well. It is amazing the difference that a low-ripple power source can make when it comes to random crashes.