I had a separate boiler for DHW (a main 7) and CH, and when my son bought the house he swapped the two for one combi, however if you have a hot water storage tank, it offers some advantages, mainly you can heat water with cheap energy, I use solar in the summer. Also there is no real limit as to how much hot water one can use, if you want 3 showers you can have 3 showers, and filling a bath is so much slower using a direct gas water heater, be it a combi or two separate boilers.
The direct water heater is made possible as the modern boiler can modulate, (turn down) however we don't want to wait for DHW to arrive at the taps, so a small reservoir of hot water inside the boiler, however when using a shower this will run out, so shower starts cold of course, gets warm, then goes cold again, and then warm again. If you select Eco mode so reservoir not used, then taps need to be turned on full to get hot water.
This was my experience in mothers house with a Worcester Bosch.
Next is how it heats the house, standard method is all radiators in parallel each with a lock shield and thermostatic valve, and a by-pass valve which will open when all radiators are satisfied, and the boiler will reduce output as the return water gets warmer.
However this will not turn the boiler fully off, so to stop it cycling all summer, we have a wall mounted electrical thermostat. This wall mounted can be simple on/off, or it can be also modulating, so it turns the boiler up/down not on/off, these modulating controls are often linked to make of boiler, although there is OpenTherm it will not work with all boilers, and some makes of modulating wall thermostats connect to the TRV's and others don't.
My last house was open plan, so one thermostat centre of house was fine, with TRV's to stop bedrooms over heating. This house however has doors on the rooms, so different control is required.
What I am saying one needs to look at a package which suits your house, and your life style, since retired the heating is rarely turned off, but when I worked, recovery time was important, one can arrange so the TRV's open in sequence heating rooms in the order they will be used in, but if only one room is going to be heated, than that radiator needs to be able to get rid of all the energy from boiler at it's lowest output.
So you need to look at the home as a whole, not just the boiler, and what do you need? I did try geofencing with Nest Gen 3, it was rather hopeless as it did not turn on early enough, and no option to set distance from home.
We call the guys who design heating and ventilation systems engineers, which to my mind means degree standard, setting up a good heating system which does not cost an arm and a leg is not easy. Yes with Honeywell EvoHome or Drayton Wiser with TRV's all electronic linked into the system and OpenTherm connection to boiler can't really go wrong. But there are cheaper methods.