Job one is look what boiler should do.
You will notice there is a range, so looking at 18 kW 5.54 kW to 18.48 kW and when in mothers house which also had a modulating boiler I found it hard to tell if the boiler was ticking over or running flat out, here with an oil boiler easy it only has one output, so if running that is output, but the return water temperature can control the boiler output.
As far as I am aware only Bosch thermostats can connect to the ebus, so tado can only switch on/off. However some thermostats use a mark/space ratio to stop over shooting it reduces the hysteresis, good idea with oil, but with modulating gas it defeats all the cleaver algorithms built into the boiler, temperature control needs to be done with the TRV head, not wall thermostat, all the wall thermostat is for is to switch off the boiler on a warm day.
I found with mothers house setting the lock shield valve was the main thing to get boiler to work well, not being a heating engineer I do not have a differential thermometer to set the temperature drop across each radiator, so I used the turn off until pipes cold, then turn on until feel the slightest bit of heat, working out from boiler, it improved things, but not good enough.
So I used the TRV the
computer shows both target and current, so if current exceeds target then close the lock shield a small amount, and after trimming the lock shields the TRV's kept the room within 0.5°C of set point and worked very well, except when other heat sources caused problems like sun in bay window.
Once set I found the radiators ran a lot cooler, as the boiler was modulating so getting a constant heat just enough to maintain the room temperature not the all or nothing I was getting before they were set. Since the radiators ran cooler, when the sun hit the bay windows they stopped heating room faster so less over shoot caused when sun came out.
My intention was fit electronic TRV heads and then a wall thermostat to control them, however they worked that well never bothered with new wall thermostat.
I did however find the built in anti hysteresis was OTT, so set the TRV at 22°C at 7 am then 20°C at 8 am to speed up reheating after being on over night, this meant the geofencing was useless, would never hit heat on time, so used simple time control.
I read the Drayton Wiser TRV head has algorithms built in to work out how long it takes to heat the room, so can reheat rooms faster without over shooting, but never tried them.
As to UFH had electric version in the wet room, totally useless, it just took too long to heat up the room, maximum floor temperature set at 27°C and that is simply too cool to heat the room, needs radiators as well.
Using geofencing the idea is speed, so iVector fan assisted radiators to reheat fast, but UFH is slower than standard radiators will not work with geofencing. The iVector is so expensive so I would use a plinth fan assisted in the kitchen, but standard radiators in other rooms, the plinth fan assisted does warm the floor so no need for UFH in kitchen.
But remember I am an electricians not a plumber or heating engineer.