Buyer's Guide: "port’s use impinges on eGPU PCIe bandwidth"
I'm referring directly to this quote from the Buyer Guide:
I just realized that due to the way Intel handles ThunderBolt 3 (throttling PCIe to 22Gbps on full links, to reserve 10Gbps for USB and 8Gbps for DP), there SHOULD be virtually no performance degradation if using the USB ports, or if any of the enclosure's additional ports (i.e. internal SATA) are part of the USB hub. Anyone care to comment?
The enclosure TB3 USB-C 3.1 controller hosting the additional ports is a PCIe device as shown here. Therefore it too becomes part of the "up to 4 lanes of PCIe 3.0" input to the TB3 controller combing traffic with the video card. Therefore these extra enclosure ports do impinge on the TB3 channel video card bandwidth.
Performance enthuasiasts may then choose to get an enclosure without those extra ports and host high bandwidth devices such as storage off it's own separate host port and cable as a USB-C 3.1 or USB 3.0 device.