I’m assuming you’re referring to the above screenshot of the denoiser commands. That’s just 18 available controls, not separate denoisers. Most implementations will likely have individual denoisers for each raytraced element(reflections, shadows, GI, etc) as they all focus on different aspects, and as pictured you get even more fine-grained control over their appearance and performance if necessary. Denoising isn’t something the average artist should have to worry about though, as well as the other non-denoising controls like material sorting, russian roulette, etc. as they are much more technical and deal more with the performance and not visuals.