Generally, boilers are more efficient working to hotter temperatures

Eh?

Boilers are fundamentally more efficient at lower temperatures. This isn't a
design issue, but stems from the laws of thermodynamics. This is in addition
to the extra efficiency from condensing.

The only reasons for having high temperatures are (a) your heating won't
actually work well enough and (b) your non-condensing boiler with condense
and rot from within.

Christian.