Digital thermostats for underfloor heating: useful? Is the extra cost justified?

I am currently setting all rooms via the HKVs as we do not have ERR (wanted) If that is done, one would never change anything there, right?! But when I read here that pyrotechnics run 25-26 degrees in the bathroom, that's really insane??? We have just under 23

Of course, you can also change temperatures afterwards, just not in the way you do with RTRs, but as experience shows, this is not necessary either. 25 degrees in the bathroom is not a big deal now.

In the children's rooms we actually actively regulate the temperature with the RTR. On weekends it is turned up and on other days turned down. It has nothing to do with frugality, but the children sleep significantly better below 20 degrees (so do I), and playing in the children's rooms usually only happens on weekends. I have been used to higher temperatures in the bathroom for some time and find that very pleasant. In the living room I cannot regulate the temperature via the HKV. The required power is very low on the ground floor on the southwest side and the flow temperature is quite high in the system. Therefore, the RTR switches on and off there frequently. In the sun it is always "off," so I can hardly do without it here.

What flow temperature do you run? To achieve 26-26 degrees in the bathroom, I’m not surprised that you have to run a high flow temperature. The consequence of this is that many other radiators have to be throttled --> heating cycles.

The consequence of this is that many other radiators have to be throttled-->Heater cycles.

I never quite know what is meant by "cycles," but you are probably right. It doesn't bother me, though; that's what the controllers and actuators are designed for.

Cycling means turning the boiler on and off. It has something to do with their lifespan. The goal would be for the boiler to run continuously to provide the heat.