Modest Royalty: Subverted. For a couple of reasons: first, the problem with leading people who aren’t impressed by claims of authority by right, or to put it another way, the problem with leading by virtue of your displayed arête, is that you have to display it. Second, humility is not an Imperial virtue, and pride, however, is. To be the part, it helps to look the part.
(This, of course, also applies to everyone who isn’t royalty, too.)
This is not, however, the Ermine Cape Effect, because Imperial runér from the Imperial Couple on down are the Royals Who Actually Do Something, and need to dress functionally sometimes. It’s just the right kind of functional. When doing the business of the Empire, for example, the Emperor may well be wearing something as relatively non-regalian as the US President’s suit, but it is undoubtedly hand-made (see Only Electric Sheep Are Cheap), constructed from the finest materials, and otherwise just as signifier-bearing. In other words, they can do subtle; subtle is not a problem, because their people understand and know to look for subtle. They just can’t do modest, because modest is just fundamentally wrong.
But compare: What’s Up, King Dude?