What you need to keep in mind is that a lot of USB-C Ethernet adapters run over the USB3 lines - USB has a lot of CPU overhead which becomes visible at those speeds.
USB-C, with the right cable, connector and machine, can support Thunderbolt which is PCI-Express. If you go for a Thunderbolt adapter (and not a USB-based one, as above), you will get around this problem. You can also get one of those external GPU cases and put a desktop-grade PCIe network card in there and it should work provided your computer has the drivers for it (for Mac, I'd suggest trying an Intel card and hoping for the best).
I have this setup (eGPU case with a 10GbE NIC) and what you want for a Mac is an Aquantia AQC107 card, which I’ve managed to get a few of. Those have the same 10Gb chip as Apple uses so work perfect with no issue.
USB-C, with the right cable, connector and machine, can support Thunderbolt which is PCI-Express. If you go for a Thunderbolt adapter (and not a USB-based one, as above), you will get around this problem. You can also get one of those external GPU cases and put a desktop-grade PCIe network card in there and it should work provided your computer has the drivers for it (for Mac, I'd suggest trying an Intel card and hoping for the best).