The dock contains an MST Hub that only has 2 lanes of DisplayPort input. This is because the USB-C dock uses two of the 4 super speed lines of the USB-C connection for USB 3.x.
The dock appears to have a DisplayPort 1.2 MST Hub (with only two lanes of HBR2, it can only support up to 4K30 10bpc or 1440p60 10bpc for a single display). You could try 1440p30 10bpc for two displays.
A Thunderbolt dock allows two 4-lane HBR2 connections – 4 times the DisplayPort bandwidth of this USB-C dock.
Now, if the dock were updated with a DisplayPort 1.4 MST Hub, then it could use two lanes of HBR3 for 50% more bandwidth (enough for two 1440p60 8bpc displays). And if your GPU supports DSC @ 12 bpp then you could effectively double that so you could connect two 4K60 8bpc displays or two 1440p60 10bpc displays. DSC @ 8bpp could effectively triple the bandwidth but I don’t think I’ve seen that mode before. I don’t think Windows shows anywhere what DSC compression ratio it’s using.
I think 10bpc is required for HDR (at least in macOS). Windows may allow HDR with 8bpc?
Club-3d does sell three-port DisplayPort 1.4 MST hubs that don’t contain any USB outputs. That means they can support 4 lane HBR3 input. See the CSV-1550.
If you need other ports, the CSV-1568 appears to be a dock with DisplayPort 1.4 MST Hub (2 lane HBR3 input).
The CSV-1566 uses two lanes of HBR2 for one display and DisplayLink for additional displays. Maybe you want to avoid DisplayLink if possible.
I think the CSV-1562 uses two lanes of HBR3 (I am guessing since the product page mentions DSC support, however the download says DisplayPort 1.2 which means HBR2) for one or more ports and DisplayLink for other ports (the documentation is inadequate). The documentation doesn’t say if it has MST Hub functionality (to convert two lanes of HBR3 to four lanes of HBR2 for 4K60 10bpc displays that don’t support HBR3). The documentation doesn’t say what ports use DisplayLink. Maybe DisplayLink is used for the DisplayPort 1.2 ports and MST is used for the HDMI ports?