If the smart valve is paired with a room thermostat then I would expect temperature control for the room to be good. Might be worth contacting Tado directly to see if they can account for the large overshoot in temperature.
It’s normal for the system to overheat the set point a bit, but by 1.5°C is excessive. Do you have smart TRVs on some radiators? These can request heat and cause rooms on the same circuit without a smart TRV to overheat.