2800 MBps is ~ 22Gbps and while that's pretty fast I think "world's fastest" may have been a year or two ago because the Sabrent PCIe 4x4 4TB NVMe drive I had to buy for my PlayStation has read speeds over 6000MBps. In my Express 4m2 enclosure rated for 2800MBps I didn't spend that much for the fastest ones I could get mostly because the enclosure's limit means most of that extra performance wouldn't be realized. I don't know if there are any external enclosures for multiple NVMe devices that opens up enough lanes to actually hit that top speed.For the Gigadrive that is now delayed, since it uses Goshen ridge, and has only 1 Pcie lane, you’re saying that the 2800 MBP/s is channeled only through that 1 lane? (Confused because you’re saying that it would be limited to 750 mb/s)
One thing I haven't seen benchmarked is multiple Thunderbolt NVMe devices connected to the same Thunderbolt port of an integrated Thunderbolt controller (Ice Lake, Tiger Lake, Apple Silicon) since integrated Thunderbolt controllers don't use real PCIe (they are inside a CPU so it doesn't need to be limited by PCIe) they won't necessarily be limited to 3500 MB/s. So in this setup while the max of each Thunderbolt NVMe device will be ≈2800 MB/s, they might have a higher total up to 40 Gbps.
I'm an edge case; my Express 4m2 enclosure is a zpool and benchmarking that is really hard to do accurately or comparably because of the ARC cache in addition to what macOS might be doing. I took a cruise through ioreg and nothing stood out in terms of the thunderbolt/pci hardware, it looks like it's using what is provided by the CPU on the macmini8,1 I've plugged it into. I have one bus (port1+port2) dedicated to an Akito Node Titan eGPU at 4x lanes and then my OWC TB3 dock and OWC Express 4m2 plugged in to port3+port4.