@macottom I am going to answer you here in this other thread since the reply was more relevant here.
You asked several questions in your thread titles “Stock sonoff Zigbee 3.0 stick” but answers to those questions are really general to all Zigbee Coordinator adapters and Zigbee Router devices in general.
Highly recommend reading all the tips my original post in this thread → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
Yes your Zigbee devices will resolve all network routes by themselves automatically, but you need to be aware Zigbee relies on network mesh technology and all deceive signals are very weak, so you can not only add Zigbee end-point devices to your network as those will not help route any traffic or extend the range and coverage. Instead, you need to add products that also act as Zigbee Router devices (which most mains-powered devices are) as those will route the traffic from other devices to build out your Zigbee network, extending the range and coverage
I personally do not recommend buying Zigbee lightbulbs that act Zigbee Router devices unless you remote the dumb switch that can turn of the power, because your Zigbee network expects that all your Zigbee Router devices are always available and therefore a Zigbee end-devices connected indirectly through a Zigbee Router device usually takes 1-hour or longer to reconnect (and some Zigbee end-devices with buggy firmware will sometimes never reconnect to other Zigbee Router devices than it was initially paired with).
If you want to control ceiling lights then a better option is buying smart Zigbee switches and/or dimmers to control dumb lightbulbs (though you might need to also buy other dumb lightbulbs if get dimmers).
If you are just starting out I suggest you consider buying a few dedicated Zigbee Router devices. Again, recommend try follow this extended guide to get started with a best practice setup/environment from the very beginning → Zigbee networks: how to guide for avoiding interference and optimize for getting better range + coverage
It depends which model you bought and firmware used, but in general most modern Zigbee Coordinator adapters (like those based on CC2652P/CC1352P and EFR32MG21 SoC radios from Texas Instruments and Silicon Labs respectively) can handle controlling around 100-200 Zigbee 3.0 devices (depending on your setup and environment) or thousands of older Zigbee devices that are not using Zigbee 3.0 security features, (the reason they can not handle more Zigbee 3.0 devices is that it has a higher security overheard and the current generation of SoC radios do not have enough RAM, so that could be higher with newer Zigbee radio SoCs in the future). Regardless of which Zigbee Coordinator adapter radio is used, they can not connect to all devices directly, you are going to have to add Zigbee Router devices to extend the maximum number of devices that can be added to your network.
ZHA docs explain most need to know about how Zigbee works (like how it depends on mesh network):
Especially read and try to understand all in these sections from the ZHA integrations documentation:
- introduction
- using-router-devices-to-add-more-devices
- knowing-which-devices-are-supported
- best-practices-to-avoid-pairingconnection-difficulties
- zigbee-interference-avoidance-and-network-rangecoverage-optimization
If nothing else then avoiding interference remember network mesh is the key and simply adding more and more Zigbee Router devices to your network will make it more and more robust.
PS: Note that ITead sells two Sonoff branded Zigbee dongles/adapters that are based on different radios. For more details see the existing threads about Sonoff ZBDongle-P and Sonoff ZBDongle-E: