I have both the official cable and one I bought a 3rd party 16ft one specifically for Quest Link off Amazon for $36
Both of them give me 2.8Gbps when connected to my 2080Ti USB C Virtual Link port. But both of them give me 1.8Gbps when I connect them to a USB C 3.1 Gen 2 port either on my motherboard (ASmedia controller on Asus MB) or from a PCIe expansion card I bought from Sonnet that has 2 USB C 3.1 Gen2 ports (also uses an ASMedia chip)
Honestly I'm not sure why the 2080Ti port gets better speeds than the other 2 ports I described above that are both supposed to be 10Gbps ports just like the 2080Ti port is.
Either way the official link cable performs the same as the 3rd party cable that is 16FT but also the 3rd party cable is a bit stiffer, thicker and heavier cable. So the $80 official one is more comfortable basically between these 2 cables anyway.
What annoys me with my setup though is when I can finally get my hands on a 3080 or 3090 GPU it won't have that Virtual Link port anymore so I will be stuck with one of these other USB ports that are 1.8Gbps.
That's interesting to know. As I have an AMD GPU, I do rely on the motherboard USB or the additional Asmedia USB C PCI-e card. Do you have any USB 3.1 Gen 1 ports? As tests have indicated (tested independently by myself and friend), the Gen 1 port can provides a higher throughput.
My 3rd party cable is actually thinner than the official cable as shown in the picture below (Left - Official cable, Right - 3rd party). Consider the official cable here in UK is £79.99, it begs the question whether it's worth buying this cable when 3rd party cables work just as well, or better in my cases.