  Environmental noise plays a key role in determining the efficiency of
transport in quantum systems. However, disorder and localisation alter the
impact of such noise on energy transport. To provide a deeper understanding of
this relationship we perform a systematic study of the connection between
eigenstate localisation and the optimal dephasing rate in 1D chains. The
effects of energy gradients and disorder on chains of various lengths are
evaluated and we demonstrate how optimal transport efficiency is determined by
both size-independent, as well as size-dependent factors. By discussing how
size-dependent influences emerge from finite size effects we establish when
these effects are suppressed, and show that a simple power law captures the
interplay between size-dependent and size-independent responses. Moving beyond
phenomenological pure dephasing, we implement a finite temperature
Bloch-Redfield model that captures detailed balance. We show that the
relationship between localisation and optimal environmental coupling strength
continues to apply at intermediate and high temperature but breaks down in the
low temperature limit.
