Does this integration give advice or does it also apply changes to the thermostat?
Could you please explain some scenario’s why I should install this integration?
The SunToPump automation sets the thermostat so that the heat pump uses as much excess solar power as possible. Since the house becomes warmer, the heat pump will work less later when that excess isn’t available. It does this by learning the power consumption for different temperature combinations. The Quatt is particularly predictable since it mainly uses outside temperature, room temperature, and thermostat setpoint to calculate the required power.
It’s also possible to only get advice from SunToPump, as you say. Just toggle SunToPump active off. You’ll still have the suntopump_setpoint value (it’s a template sensor), which is the input for the automation.