Question about be quiet! Dark Rock Pro 4

Yes, it's enough, it just depends on how far you push it:)
I also have the same cooler for an 8700k, also headed. I overclocked it on a trial basis and it didn't cause any problems. I always head the CPU because the heat is dissipated better, which can also be worthwhile at standard clock speeds (heat is dissipated better, CPU gets less hot, fans are (slightly) quieter).
And if you run the CPU for 5 years, it certainly won't hurt if it always ran 8-10° cooler.
Remember, though, that the warranty goes away at the same time as the head.