displayRole versus displayFormat

[haggis999]

I am attempting to create some notes to remind me of the exact purpose of each of my MinimServer settings, which have evolved over several years.

The following two settings are causing me some confusion, as they both appear to do the same thing, i.e. to make the Playing Now screen on my various controllers show the Composer name in place of the Artist name.

tagCustom=Composer.displayRole={artist}
tagFormat=Artist.displayFormat={$composer}

I would appreciate some clarification of the difference between these displayRole and displayFormat settings.