The PCIe lane of the SoC and the video signal output are different and therefore irrelevant.
USB-C can transmit video signals even if the SoC does not have a PCIe lane (like a smartphone).
USB-C has a high-speed 4-lane signal line (and a separate low-speed line for USB 2.0).
Switch between data and video.
However, if the USB 3.x data line and video signal are used simultaneously, the video signal is halved.
DP1.4 Full Speed max 4K 120 Hz, 8bitSDR YUV444 or 10bitHDR YUV422
DP1.4 Half Speed max 4K 60Hz, 8bitSDR YUV444 or 10bit HDR YUV422
Probably.
However, DP1.4 has a video compression technology called DSC.
Therefore, Half Speed is not an issue if it is supported and restored in the dock.
Of course, DP2.0 does not require DSC.
https://en.wikipedia.org/wiki/DisplayPort