It depends what else is going on in your environment, in particular what channel your WiFi network is on, so there’s no one answer.
I like WiFi 11 and Zigbee 11 because it’s easy to remember and these two are actually far apart. Some people like to start with zigbee channel 20 because it sits in between two WiFi channels. But I don’t know how Thread factors in on a ST hub (it uses the same channels as Zigbee).
FAQ: Networking and Reducing Channel interference between WiFi and Zigbee
The newest devices use a hardware system optimized for co-existence. In particular, Zigbee will tell the WiFi controller it needs to message and the WiFi transmission will be very briefly paused to let the Zigbee messages through. But I’m pretty sure the ST hubs are not using this technology. 