Heating curve: boiler and/or mixer?

We have been living for a few years in a mid-terrace house with an oil heating system (including hot water). I adjusted the heating curve to our sense of warmth in the first winter and have been trying to optimize it further in the following years. Since oil has now become very expensive, I wanted to approach the whole thing a bit more ambitiously.
From the previous owners, there is a heating curve set for the boiler circuit and one for the mixer. The mixer was always a few degrees colder than the boiler. I have kept it that way.

However, from my point of view, we only have one heating circuit. Directly behind the oil heating system is the mixer. The mixer has two "inputs" (from the burner and the return flow) and two outputs (to the burner and into the heating circuit). Now I am wondering whether it makes sense to have the boiler always heat warmer than the mixer then mixes? Would the heating curve of the mixer alone perhaps be sufficient? Or does the boiler then shut down completely?

The heating system is an Elco Klöckner with a LOGON M controller.

Thank you very much for your help.

What else is connected to the heating system? Underfloor heating throughout the whole house? Please provide a bit more information.

Radiators with sections are attached to the heating system. In the bathroom, there is a bathroom radiator/towel radiator. Otherwise, there is also hot water connected to the heating system.