Boilers are kinda on/off, from a control perspective. The boiler heats water to the set flow temperature, pumps it around the loop, and repeats until it's switched off. The amount of gas used is modulated by the boiler to make the water come out at the right flow temperature. Unless all the rooms in your house are perfectly insulated, or so badly insulated that they lose heat instantly, ad-hoq temperature changes in individual rooms is tricky to do well.

I did have smart TRVs for a while, but actually ended up binning them. So my current solution is: HomeAssistant controlled call-for-heat. This is a relay that when connected, turns the boiler on. Temperature sensors in each room. This allowed me to balance the radiators so they all warmed up evenly, and also feed into the HA thermostat to decide when the heat needs to come on. Manual TRVs in each room set to slightly above the normal target temperature. So they're normally open, but will close if something crazy happens, like someone turning on a fan heater. Timed target temperatures in HA. So the target temperature drops at bedtime, and rises just before I get up.

I also lowered the flow temperature of the boiler, which improves efficiency. I'm not 100% sure what you're trying to achieve in your setup. But adding TRVs to each room (and having one always-open, like the bathroom) would be a good step forward.