I think another thing to consider when we are discussing "traditional" vs. "historical" is the overall outfit.

As Rathdown stated, a four yard box pleated kilt worn with a Crimean War jacket is "historical" as it becomes part of a recreation of an historic outfit. The same kilt worn with a Prince Charlie jacket is "traditional" because it is part of a contemporary evening wear ensemble.

For another example, consider this sporran:

This is an eighteenth century sporran (the cantle is, no doubt the leather has been replaced at some point). As such, it is an historical piece of Highland wear.

This is the outfit it is being worn with, however:

(Sir Malcolm MacGregor, chief of the clan, with his wife Lady Fiona MacGregor, at the Stone Mountain Highland Games last year). This is not an historical outfit. Sir Malcolm is not participating in a reenactment. He is dressed in contemporary daywear. His sporran is simply part of the overall outfit, and is being worn in a "traditional" fashion.

Many of the sporrans I own are modelled after historic styles. I frequently wear four yard box pleated kilts made in an historic style of pleating. I have a Victorian-era style waistcoat I frequently wear for formal wear. I've also worn a nineteenth century replica shirt, collar, and cravat for formal functions. Yet I wear each of these things as part of contemporary Highland dress daywear or eveningwear, with no attempt at historical reenactment. In other words, I am not trying to recreate the look of a particular era with these clothing items. Rather, I am bringing these older styles up-to-date by wearing them with contemporary dress.

Highland fashion allows for a lot of historical "throw backs" in your style. But it's the outfit as a whole, in my opinion, that determines whether you are dressing historically or traditionally.