GPU at 99%, CPU low
AAA at Ultra usually limits on the GPU. If raising resolution drops FPS hard, the GPU is the cap. /comparar/gpu shows jumps between models.
Practical signals using game pages and the comparator — no mandatory third-party tools.
CPU maxed, GPU idle
E-sports, sims and open worlds with crowds (Cyberpunk, Helldivers 2) punish CPU. If lowering shadows does not raise FPS, check /comparar/cpu before a new GPU.
Use per-game verdict
On each page compare your current combo with a better CPU and a better GPU. Upgrade whichever moves the verdict most on games you actually play.