So you mean rather increasing the upper buffer temperature so that it is reloaded more often, than heating up almost the entire buffer. So rather keep an eye on maintaining 75 degrees at the top, and about 60 degrees at the bottom (which is sufficient for underfloor heating).
No. I meant that it is probably irrelevant as long as the losses from the storage etc. remain inside the house and thus relieve the actual heating system. The losses that leave the house through the chimney must be minimized by appropriate operating methods during combustion. Unfortunately, I cannot help with how exactly to achieve this. If the technology is located somewhere in the basement of the apartment building, storage losses there are probably also "lost" and should be contained or taken into account. With solar thermal systems, low temperatures in the storage are beneficial so that the heat from the roof is also accepted.