The dock does provide the ports to connect to monitors, but what gets displayed is still the task of the GPU in the laptop. The GPU creates the images for the screens and sends that information as a digital data stream to the dock, where it's decoded by the dock hardware into DisplayPort or HDMI compatible data streams for the connected monitors. Here's a
link to a teardown of the dock, with some pretty block diagrams of how it all goes together.
Performance will be limited by the speed of the GPU - how fast it can paint all the pixels needed for the multiple displays (including the laptop screen if you use that as well as the two monitors), and the speed of the connection to the dock and bandwidth within dock itself - it needs to transport and decode all that data for the two monitors fast enough to give you an acceptable refresh rate. The laptop is new, has Thunderbolt 4 which the dock supports, and a quick look at the specs suggests you shouldn't really have any issues running 2 x QHD displays if it's mainly for work use, spreadsheet wrangling, video calls and so on.
In my previous post about that customer with the dual 4K screens, I had a 10th gen Intel laptop connected to their dock via USB-C 3.2 Gen 1 interface which only supports 5Gbps, so that was probably why it struggled with the two 4K displays. I've just looked up my laptop's specs and see that it has a second USB-C 3.2 Gen 2 / Thunderbolt 3 port with 10Gbps bandwidth. Using that port instead would have helped.