For animation with Cycles it is generally recommended to enable that button to get random noise pattern in each frame. Otherwise you will get an annoying visible static noise pattern.
Now with Denoiser… I’m not sure that flickering is only produced by the noise pattern of the render. My doubt is about objects with noisy materials moving. And also about whether any possible remaining static noise may end up being more annoying than flickering. Anyway I am not sure here, I would need to do more tests. Edit: I’ve done a little test, apparently it’s better static noise pattern. But be sure to use high sample rates and proper denoiser settings to not get static patches.
For now it is advisable to render with high sample rates if you are going to use denoiser. Suppose your scene requires 10000 samples to render normally without any noise. Well, if you are going to use denoiser with Radius=5 for example, try with 8000 up to 6000 samples, but not much less than that.
Then when cross frame denoiser is implemented, we may be able to reduce much more sample rates.
Also as the documentation mentions, perhaps it may be appropriate to use use “Correlated Multi-jitter” as a Pattern method.