So if you're using the shared files, there's not much you can do - especially for large numbers of small files.  That's been a challenge since Fusion 1.0 (though they've made huge strides since then).

The best option is to directly connect the drive to the VM as a device.  But Fusion won't virtualize USB 3.2 or thunderbolt connections, so there's a bandwidth cap there too because of 3.1 limitations.

Honestly, if you need 8GB/sec performance, running windows native is probably the only realistic option.