Boiler Temperatures

Depends what you designed the system for. Not enough info.

If it's a condensing boiler, you set it as low as possible which still heats the house adequately. The perfect temperature is just low enough so the room thermostat never quite has to switch off. This will change depending on outside temperature though, and you will also need to raise it initially to get a cold house up to the right temperature (the more sophisticted boilers do this adjustment automatically).

If it's a non-condensing boiler (which are not legal to fit anymore except in a few very specific circumstantes), then it should be set similarly to the above, except the return water temperature must be at least 60C in order to prevent condensation and corrosion in the boiler.