I don't expect it to be any faster than 15% in any case since cores don't scale linearly.If these are the actual numbers then 3090 is only 10-12% faster than 3080 for more than double the price
Some in-game benchmarks do show 24gb ram so if true its awful. How could they claim 8k.
The difference will come when both the GPUs are bandwidth limited or when the 10gig frame buffer becomes a bottleneck.
This card is primarily for developers and deep learning guys. No point for pure gamers buying this.