A thermostat on the wall in some houses can control the whole system, in my last house for example that was the case, open plan house, large arch between living and dinning room and no door, so thermostat near the arch controlled down stairs, and upstairs always hotter so the TRV heads stopped upstairs from over heating.
Mothers old house and this one, wall thermostat is really there to stop boiler cycling in the summer, the TRV heads should control room temperature, however I don't like it hot at night, so I want heating turned down, and with an oil boiler that means unless I use the wall thermostat boiler will cycle off/on all night, so use the wall thermostat to program night switch down, but not really a good system, as in the morning the heating has a tendency to over shoot, so have to set wall thermostat to raise 0.5°C per hour, so it does not over shoot, as the hall is slower to cool than other rooms, so if it over shoots then other rooms are cold before the central heating fires up again.
The Hive system would cure this with its demand for heat, but now Nest Gen 3 installed I don't intend to rip it all out and install another system, the idea was the Nest wall thermostat tells the Energenie what heat to set, but that is flawed, for many reasons.
1) Often the Nest fails to change the TRV setting, seems support has been withdrawn.
2) In Winter since Nest is near centre of house and higher on wall to Energenie they don't show same room temperature, at moment Nest shows 19°C heating to 19.5°C and Energenie shows 15°C heating to 20°C, so 4°C different between the two, but summer when heating not on they show the same, so not calibration it is simply how the thermals move air in the hall.
3) Nest only monitors temperature in the hall, if any other room gets cold, they stay cold as TRV can only heat room when the boiler is running.
So four rooms all with heating lead onto the hall, so hall is the clear selection for all round control, and heating rates can be controlled by the lock shield valve, so it can be set so hall heats last, but we have no control on cooling rates, so if a room is too cool heating will not run until hall cools.
Mothers house cure was two wall thermostats in parallel, one in hall and one in kitchen, so if wind direction caused hall to be slow cooling then the kitchen wall thermostat would still fire up heating. However the big difference was she had a gas modulating boiler, so instead of switching on/off, it turned up/down, so the heating was running for longer, so more able to respond to a demand from a TRV head. So due to modulating boiler the temperature did not over shoot so every room with a electronic TRV head stayed at temperature set, the only problem was the Energenie heads had OTT anti-hysteresis software, so in the morning had to cheat and set to 22°C for one hour then 20°C or half way through morning before room hit day temperature.
Evo Home, Drayton Wiser, Hive, Tado all have the TRV telling main hub/thermostat what to do, there is also with some two way so the hub/thermostat tells the TRV what setting is required, but the TRV tells the hub/thermostat when to fire up boiler, or with OpenTherm what temperature to set boiler to, Hive is odd one out in that it can't work with OpenTherm, but Nest is odd one out that it only measures the temperature in one room.
EPH is also an odd one out, EPH as far as I can see is the only system designed to work with motorised valves dividing the system into zones, all the others use the TRV heads to divide into zones, with EPH one wall thermostat is set to master, and others as slaves, so it controls the motorised valves on/off, but still controls boiler up/down with opentherm. I seem to remember reading limit of 10 zones? It seems this is the only system that can run a condensate boiler to extract latent heat, and work on/off zone valves. Every other system seems to be designed for zone valves which gradually open close, i.e. the TRV.
The problem is wrong control can still work, it just does not work in an efficient manor. And the oil, gas, or any other fuel bill will vary year to year so unless you have two identical houses with people living identical life styles you can't compare. Even on an estate of identical houses, they don't stay identical and life styles are unlikely to be the same.
In my mothers house there was nothing on the Worcester Bosch boiler to say what rate it was running at, as the user I had no idea if running at 30% output or 100% output, and to read gas meter not really any good as running other gas appliances would mess it up. I could by removing the FCU and replacing with plug and socket measure how often my oil boiler runs, and since it does not modulate run time equals output.
But in real terms we guess as to which system is best.
As to wireless controlled motorised radiator valve, you have missed out the two thermometers built into the valve which measure both water and air temperature and use the water temperature to compensate the air temperature reading and then thermostatically control the flow to control temperature output, and the algorithms used within the valve to stop any hysteresis, the wireless link may tell the valve head what is required, and also tell a hub what is happening, but it is independently controlled within the head, even if wireless link lost, it will still work.
There are very similar wired heads used with under floor heating which are just motors opening and closing valve, but the TRV head is much more than that.
show current under target then boiler should run, and only when all are satisfied should boiler stop. There is no need for the wall thermostat to be connected to internet, only the TRV heads need to be connected to internet, so you set each room, and they tell the hub/wall thermostat if boiler needs to run, and that tells boiler.
