Besides copying large files, do you have an app that can consume 2 GB/s? That's more than two streams of uncompressed 4K.
(I'm currently looking into solutions like a custom filesystem driver, running a second VM and using internal networking to stream to a FUSE filesystem, or possibly even hooking the filesystem access of my debugger and inserting a compression step into WriteFile() calls)
I don't have to move 10GB+ files to know if my network is 10MB/100MB/1000MB/10G0B. The speed it transfers is representative of my network speed be that file 4k, 10MB, or 100GB.
The same is true for all transfer speeds.
:.:.:
Also yes there are diminishing returns with information requests, acks, etc.
There are plenty of applications that are still disk IO constrained at those speeds.