30 years ago our boiler were not condensate type. Please let me explain. Today the return temperature of the water to the boiler controls the flame height. 30 years ago a boiler was simply on or off that is no longer the case.
So cold house boiler switched on all TRV wide open and the flow through each radiator is controlled by the lock shield valves so temperature drop is same for all radiators in the system and the by pass valve is closed.
As each room warms up the TRV slowly starts to close, old type did tend to snap closed and had to be correct way around so they did not hammer but new types slowly close, this pushes more water through those radiators which have not started to close so return water gets warmer.
As even more TRV start to close or fully close you reach a point where by pass valve opens so return water again gets hotter.
Now the boiler measures the return water temperature and as it raises if reduces flame height until it can't reduce it any more at what point it starts to cycle off/on, with the better boilers every time it restarts if tests the return water temperature and if still hot it increases off time and if cold decreases off time reducing how many times the boiler cycles.
I has to work this way because unless the return water is cool enough it will not gain the latent heat of evaporation from the flue gases.
So today we have to have something on the radiator to control radiator output as the return water temperature controls the boiler, it does not need to be a TRV it can be fan speed, with fan assisted radiators you don't need the by pass valve and instead of controlling flow the fan has 3 to 5 speeds which vary according to how close the room is to set temperature. Net result is the same every room is individually controlled.
However when Summer arrives the boiler would still cycle unless some one switches it off, so there are various ways to automate the summer switch off, simple is for human to flick a switch, fan assisted radiators need a building management control which could also control cooling, non fan assisted could use a central thermostat which is linked to each TRV so once all valves are satisfied the boiler is turned off, and if boiler has opentherm then first it turns boiler down then off, the is the Honeywell EvoHome system.
There are cheaper systems where the TRV and wall thermostat follow each other the advantage is should a TRV be programmed to call for heat at 6 am after being dormant over night then it will tell the wall thermostat which in turn tells the boiler to fire up, or you could have rooms calling for heat but the boiler is not running.
However with some careful setting so TRV open just before the main thermostat also calls for heat you can get around this problem. Also setting the TRV to say 24°C at 6 am then down to 20°C at 8 am means on the change of temperature the valve is wide open so change is faster.
I am unaware of what are good quality valves and which are poor, maybe some plumber can tell us? But with the heads you have a whole range some with bellows, some with wax and also some using small electric motors. Those without motors normally have simple numbers on them you can't set them to 20°C as not calibrated much depends on air flow, however those with electric motors have two sensors one measures water temperature and the other air temperature so air temperature reading is compensated for the heat from radiator by measuring water temperature, so since I have two I can say set to 20°C the room will be between 19 and 21°C unless something else heats the room like sun through a bay window. So cheap electronic heads are stand alone, more expensive with talk vie a hub to your phone or PC, and may support IFTTT so also talk to a thermostat like Nest, and then the top quality ones connect to a central thermostat that is the Evohome.
Because the return water temperature to boiler is not so important you really can't do without TRV, or multi speed fans. You really have no option, all you can do is decide what quality of valve or radiator to buy. However that does not mean every radiator need to be top quality, in my open plan house I have one fan assisted radiator and because it circulates the air I get away with it, plus TRV upstairs.
Mothers house where I am now has two radiators down stairs with eTRV and 6 standard TRV's on rest of radiators, however the bay windows are a problem with her house.
My first house had a single thermostat, the gas hot air heater was under stairs and it sucked air from living room and blow it to every room in ducts, then had vents in every door so air returned to living room, and every room was same temperature. But unless you have fans to circulate air then you can't use one thermostat.
What surprised me was how slow the house cools, I was not getting rooms to cool down, I thought the TRV was not turning off as it should, however I set the old programmer to switch off whole boiler at 10 pm and back on at 6 am, don't know why I bother as by 6 am when ready to switch on again I am lucky if the house even cools 2°C so although in theory the house is set to heat up and cool down in different parts of the day, in real terms it does not happen, it hold the heat far too well.
