Both interfaces have almost the same raw bit rate (in both cases "10 Gb/s" is only an approximation, but the differences between the true bit rates and 10 Gb/s are negligible, unlike for "5 Gb/s" USB, where the data bit rate is only 4 Gb/s).
The USB protocol has a slightly higher overhead than the Ethernet protocol, so the throughput of an Ethernet 10 Gb/s interface attached on 10 Gb/s USB will be a little lower than that of a PCIe NIC, but the difference is negligible, of only a few percent.
USB 4, i.e. Thunderbolt, allows the emulation of network interfaces if you interconnect the USB Type C ports with a cable, but here you have USB 3, so this does not work.
On USB 3 you could interconnect 2 ports only if one of them implemented the On-the-Go specification, so it could work as either a peripheral port or a host port. Here this also does not work. On a system where this had been allowed by the hardware, it is likely that you would have needed to write yourself a device driver that emulates a network interface, because I am not aware of an already existing one, unlike for USB 4.
USB4 and TB are different things (confusingly enough)
All features of Thunderbolt 3 have been inherited by USB 4, like also all those of USB 3, including the ability of Thunderbolt to emulate Ethernet interfaces when you interconnect 2 computers with a cable through their USB 4 ports, like it was already possible with Thunderbolt ports.
But I really apprecate your reply!
I'll definitely buy one for testing when they become available for reasonable prices <500EUR for 16gig memory