Yes, the Thunderbolt 4 port is compatible with the HP USB-C Docking Station G5, as Thunderbolt 4 is backwards compatible with USB-C. The G5 supports USB-C and DisplayPort Alt Mode over Thunderbolt, so you can easily connect peripherals via a cable without having to reconnect everything. Make sure you have the latest drivers for optimal performance.
According to our information, the Intel Core Ultra 9 285K has no integrated memory. The 128 GB RAM is a traditional 4 x 32 GB U-DIMM DDR5 configuration on the mainboard.