So far SmartThings is only officially available in the US and the UK. And maybe Canada, which uses the US version.
This introduces an immediate problem, as Zwave operates on different frequencies in different geographical regions, and the frequency for Hong Kong is different from that of both the US and the UK.
In some countries it is illegal to use a zwave frequency not specify for that region, as it might interfere with the band reserve for ambulance communications or something else of public interest.
So the first thing you need to do is find out if either the UK or the US zwave frequency is legal to use where you are. (In part because of these legal restrictions, the zwave frequency is set at the time of manufacture, and cannot be changed afterwards. ) if only one is legal, that tells you which model of the hub you need to get.
Selecting Light Controls
The biggest issue with switches is usually the question of whether a neutral wire is available at the switchbox. Most home automation switches, although not all, use the neutral wire to power the home automation radio in the switch so that it will be able to hear the next “on” command from the network even though this switch appears to be off. However, while it is pretty common to have a neutral wire at the switchbox in the US, the same is not true in other countries. So you will see a lot of discussion in the UK category over " two wire" (no neutral) and “three wire” (with a neutral) switch box setups.
As far as specific options , see the UK lighting FAQ for discussion of the various standard options for 220v.
Zigbee Profiles
With regard to zigbee, it is important to note that there are a number of different zigbee “profiles” and they do not all communicate with each other.
Smartthings uses the “zigbee home automation” (ZHA) 1.2 profile. Devices which are also actually certified for that profile are the ones That have the best chance of working with SmartThings. Zigbee devices are very popular in China, but many use a proprietary form which will only work with that brand, and others use zigbee green power or other profiles which will not work with smart things. This also happens in the US. For example, control4 uses a proprietary encoding which does not work with SmartThings. Often these devices will pair to smart things as a “thing” but then cannot be controlled or lose connection every few hours and have to be rejoined to the network. You can find much discussion of this in the forum under threads dedicated to some of the inexpensive Chinese brands like Xioami.
(The smartthings hub is one white plastic box that includes both a Z wave controller and a zigbee Coordinator. )