This will probably be the same as with Aqara or Apple. You specify the main router for Matter and/or automation, and so on, but the Thread Border Router is automatically selected according to the Thread standard.
I assume that the Thread Border Router with LAN will be selected automatically, as this will have the lowest latency. However, under unfavourable circumstances, the WLAN hub can also be selected as the primary Thread border router.
That was the only thing I could find. However, it still sounds very vague.