If you want to get really pernickity (is that how it’s spelt ?), you could say that a glengarry or balmoral may only be seen as representing the descendants of the Hanoverian Crown if the black cockade (ie the silk rosette) is worn on its left side, as is the case with the RRS. Many civvy hats are available without the cockade/rosette and it can be removed from those which have it.

As for bonnet-tails, the balmoral issued to replace the glengarry in Spring 1915 for Scottish infantry regiments was close-fitting like a modern British Army beret, knitted plain dark blue overall (no regimental dicing at all) with black silk-like bow-tie and hanging, ribbon tails and with a red toorie. To the best of my recollection, there was no cockade. In the trenches, it was worn under a khaki cotton cover (without toorie). In late 1915, it was replaced by the voluminous all khaki sewn cloth Tam O’Shanter with khaki wool toorie, with short tails tied in a bow with no hanging portion left over. Again no khaki cockade, though I used to have a Royal Scots officer’s WW1 dated ToS which did have a khaki silk cockade. Presumably an officers’ tradition.

Up till 2006, the dark blue Black Watch balmoral didn’t have either a rosette or tails (see my album). Presumably, the rosette would have looked odd in front of the red hackle with no badge. The red hackle is fixed internally via a little hole in the left side of the bonnet rather than being fixed behind a badge.