 Solution

Use small multiples with consistent axes, direct cutoff labels and distinguishable line styles, with an inset enlarging the low-false-positive-rate region of the ROC curves. Add a compact summary of area versus minimum read count with uncertainty intervals and the number of eligible loci retained at each cutoff. This would make the modest ROC-area change and larger precision–recall-area change easier to assess than several nearly overlapping colours.

A coverage restriction also changes which loci are evaluated. For a clean comparison, show performance on a common locus subset as well as the practical retained set; otherwise an apparent improvement may partly reflect exclusion of difficult loci or a changed positive prevalence.