How many games, cards, resolutions does GN test?
GN uses a smaller test selection, but they test much more rigorously, report more data, and choose their test titles with very stringent criteria - for example, you test Civilisation VI for GPU reviews. I would argue that's a pointless thing to do unless this is also your CPU test bench, since Civilisation VI is almost always CPU limited, not GPU. GN would also criticise the use of Civ VI as a benchmark in general, as they've seen patches for Civ VI impact performance dramatically in the past, making their previous test data inapplicable.
GN also reports 1% and 0.1% lows in framerate, but, beyond that, they generate frametime plots like these ones, that show in a much more significant manner, issues in specific games on specific hardware.
For example, in this test you can clearly see that the 1050Ti provided not only a lower overall framerate (longer frametimes), but it provided it less consistently overall, meaning more perceptible stutter.
They test F1 2018, Apex Legends, Sniper Elite 4, Far Cry 5, GTA V, and Shadow of the Tomb Raider, at 1080p and 1440 for all games and Sniper Elite at 4K because they've found it to be a repeatable and well optimised DX12 title.
Here's a video from them outlining their own updates to their testing methodology in the first segment:
