So far i’m agreeing with what you’ve said, i’ve installed the new Gateway via Mi Home (i’m in Australia) but i’m working off the China mainland server as this is the only way to integrate the Temperature Sensors I also Bought (Aqara latest versions). Homekit Integration is fairly straight forward, it actually integrates from the Mi Home App and automatically links to Homekit.
Problem with the temperature sensors is they are slow responding like you said ,maybe it’s going through the Chinese Servers back into the Gateway (that would be annoying if so). Also on the Homekit side of things, even thoguh i named the rooms the same they don’t show up in those rooms they go to “Default Room”. It’s hard tro work out which sensor is which TBH so i haven’t moved forward to change the room in Homekit.
The gateway doesn’t come up as and option like another user said it would above and I haven’t tried integrating the temp sensors in HomeAssistant yet.