Denuvo definitely impacts performances. It will make a game that would otherwise run fine in the most powerful rig to sometimes sutters and had fps drop.
I've found drastic examples like that - AC Origins or one of the RE games - but in all of them the devs combined Denuvo with their own DRM, resulting in a literal shit show.
I mean the first Denuvo implementation was in the first Lords of the Fallen which I've bought and enjoyed without any performance problems. And that was 10 years ago, with a 13 yo CPU.
I think usually the impact of Denuvo on a modern CPU is pretty negligible IF (and only if) the devs implement the checks in a way that they aren't called super frequently (IIRC Ubisoft was calling one of the DRM checks on every frame with AC Origins).
On older CPUs it definitely seems to have a more noticeable impact. In addition there are also cases where the devs implement the checks in the worst possible ways, Capcom and Ubisoft seem to be guilty of this with alarming frequency.
All of this said, regardless of whether the impact is negligible, it's still an impact and it's still bullshit that people that pay for a game should have an inferior experience because of an anti-piracy measure.
Denuvo could also do far more to prevent their customers from implementing the DRM in a subpar manner if they actually cared about their reputation with gamers. They could easily have a few devs who liaise with studios on a more frequent basis to ensure that the DRM is being implemented in an optimised manner, but this would require both a level of effort and integrity on their part, and they have neither.
