I had the same question, then I checked dubs wiki.

Essentially if you select radiators, they have their own temp setting, they will never heat the room over that setting, despite boilers running all the time.
Remember, you need to set all radiators in the room and temp can creep over from beyond the wall.

Unless you have the option "ignore thermostat" disabled on the boiler, they won't pay heed to thermostats.
Thermostats will trigger the boiler when the temp in the room they're installed in drops below their setting and will turn off when the temp is above.