Physics and combined score.
They all count for the total, though its most likely the physics score here, which is just there because that bench scales very well (almost linearly) with core count.
It says absolutely nothing about gaming on said system. Well, maybe if you play Space Engineers or something.
Unlikely tbh. Aside from Port Royal and Time Spy Extreme, literally all 3DMark benchmarks are absolutely dominated by RDNA2 and it's traditional rasterisation strength (and doubly so for the Fire Strike range of benchmarks).
I literally can't get anywhere close to the 6900XT scores with my 3090, and my 3090 is in the top ten for my hardware configuration (3090 & 5900X) for pretty much every benchmark going.