Unless they use faster GDDR6X memory, it should be basically the same hashrate.

To hit 180MH+, you need 5120-bit HBM2e like on the A100.

Use a lower core clock like 1000. The 5600 XT is heavily memory bandwidth limited so you don't need to run the core very high.

Maybe in the early days of ZEC when mining software were completely unoptimized. It's no longer true, Ethash is so memory bandwidth bound that you can heavily underclock a regular 1070 without affecting Ethereum hash rate. ZEC and other Equihash coins on the other hand, scales pretty well with increased core count and clock speed.

But putting chips in parallel is complicated and expensive to manufacture. It's a major reason why video card manufacturers have almost always gone fast but narrow vs wide but slow when given the choice. Even the most integrated wide and slow method, HBM, remains expensive and rare.

Isn't that the opposite; that test can go up to 2000+ because it doesn't push the cores very hard and allows the GPU to boost higher because  power usage is low.

If you're willing to lose a modest amount of production and run them at lower power use and you'll easily fit 6, even 6 1080 Ti. As an example, for ZEC and 1080 Ti, when set to a power limit of 160W I get ~80% of the production as compared to when it's set to 300W.