It's an optimisation issue not a DRM issue, AMD cards are running the game just fine, but it seems a lot of Nvidia cards are having this low utilisation bug.
Best thing we can do is wait until Codemasters releases a performance optimisation patch or Nvidia to release a driver that addresses the issue.
Here's a shot from Bang4Bucks video where it shows a 6900XT fully utilising the GPU vs an RTX 3090 only using 91%, this results in the AMD card getting around 15 to 20fps more at 4K.
The second shot is from my own video showing my GTX 980 only getting 90% utilisation.
Okay now I've just all faith in everything, this is Grid (2019) showing the exact same problem. So game is literally a copy/paste of the of the previous game, also this indicates a driver problem because Grid Autosport and F1 2021 don't have the same issue. Definitely sucks because Legends is a much more complete game compared to the dumpster fire from 2019 :P
