I tried to find Tuya Thermostat, one I found not what I would call "Smart".
In general wall thermostats have many functions, and you select those you need.
1) On/off or modulating, if the boiler supports some thing like OpenTherm then better to get a thermostat which also supports it, these turn heating up and down rather than on/off.
2) With on/off we have volt free, and tied to 230 volt supply, when the boiler uses 24 volt control the thermostat needs to be volt free.
3) Internet linking allows geofencing however as I found often you can't set the distance, so of limited use.
4) So have algorithms that work out how long it takes to heat the room, so you set time you want room hot, and thermostat adjusts when to start heating, however often there is no point as wall thermostat does not control each room temperature, it is the TRV (thermostatic radiator valve) which does each room so you need those algorithms built into the TRV as with Drayton Wiser.
5) Wall thermostat and TRV can be used in one area like the hall to work together, I am sure of that as done it, without a link, but far easier if the TRV and wall thermostat are linked, in fact some wall thermostats would be better described as hubs in fact EcoHome allows you to set the TRV from the wall thermostat.
Most homes today in UK are split into zones, there are exceptions, some open plan homes don't need it, and with hot air central heating not required as the air circulates around the home, there are two ways to make zones, one is the hard wired zone valve, the other is the TRV, the thermostats tend to be designed for either/or not found one to do both so EPH do thermostats which can be set as master/slave with up to 10 wall thermostats to work zone valves and still connect to boiler using OpenTherm, But although the Drayton Wiser does an OpenTherm module this is only for the single channel version, they do a three channel wall thermostat so two zones plus domestic hot water, but then it is a simple on/off control.
There are some thermostats which seem to work wrong way around, the thermostat sets the TRV rather than TRV controlling thermostat, Energenie is one, they did work with Nest as well as their own wall thermostat but support for Nest has been with drawn, Nest in USA have temperature sensors so monitor three areas, but not released in UK, so in UK Nest only really any good when whole home controlled from one point. i.e. hot air system.
Hive is also an odd one out, only switches on/off, but does link to TRV however with a maximum temperature of 22°C so Hive wall thermostat in the hall likely works well, but not in main room when using linked TRV's.
Each system has good and bad points, and it takes some thought to select one which suits you, in the main the wall on/off thermostat is only to stop the boiler form cycling, the TRV controls room temperature and having use electronic TRV heads I can say with a modulating gas boiler they can keep the rooms within 1°C of set point, but unless linked electrically in some way, normally a radio link, it can't turn the boiler on, in theory can turn it off, but they don't so if using only TRV's with no wall thermostat the boiler would cycle on/off all summer unless you manually turned it off.
So we traditionally fit a wall thermostat in a room normally kept cool so will switch off when likely going to be a warm day, on the ground floor as heat raises, where there is no alternative heating including sun through windows, and no outside doors, don't know about your house, but my house no such room.
So we compromise, fit it in the hall, but also fit a TRV on hall radiator set lower than wall thermostat so hall reheats fast when door opened, but slows down so does not switch off wall thermostat too soon so rest of house can heat up, this does need to hall to also cool faster than other rooms, and that is the problem with this house, hall is centre of house, and cools too slow.
Selecting where the thermostat goes is not easy with some homes, so having the wall thermostat connect to temperature sensors be them independent or built into the TRV is the easy way to set up the home.
I made a mistake, I got Nest Gen 3, which I was told at time connected to Energenie TRV's but does not, and the geofencing switches between eco and comfort settings, but seems to have no way to set distance, it has really clever algorithms, non seem to work in my home so all turned off.
So for you step one see if boiler supports OpenTherm, if not supported, does the boiler have its own modulating thermostat option, then consider how your home is used, I for example when still working had the kitchen heating switch on, followed after 20 minutes with dinning room, then 20 minutes living room, and then 2 hours before bedrooms, the delay room to room resulted in kitchen warming up faster, but not too much delay or boiler would turn off or down, I have 9 programmable TRV heads in the house, 4 energenie and 5 eQ-3, non are linked to my Nest Gen 3 thermostat, in hind sight would have been better with Drayton Wiser, or Honeywell EvoHome or even Hive, but not worth the expense to change now. I cross fingers and hope the Nest temperature sensors will be released in the UK.
I found it takes around an hour to heat from cold to reasonable level, which is longer than it takes to drive home from work, so in real terms simple time works better, odd one out however is in the summer I do check temperature at home when shopping and turn on the AC manually with phone if room too hot, I have AC vented through the chimney so no security risk, but it needs a bottle to collect the condensate, so don't want it to run automatic, as could come home to a pool of water on the floor.
Hope you learn from my error, and ensure your wall thermostat does connect to TRV heads if your home needs it.
