It's interesting to compare the way we apply ruched trims to reproduction historical garments today, as opposed to how it was once done. Perhaps this is due to the fact many no longer have the same finishing tools readily available, like pinking irons, and edging trims (or the skills to produce them). So we sometimes rely on just putting a deeper gather on our ruching, or more stuff on a gown to fill in the space.
Below as an example, we see that there isn't an excess of stuff gathered to the point of snapping the thread that binds it. Instead it's laid down delicately by hand, with just enough body to give it depth and allow a serpentine curve while laying flat.
Of course for this trim I'm sure a lower profile of ruffle was desired, and it has been flattened a bit over the ages. But even on gowns where more fulness of trimming was needed, there is still a quality of 'less as more'.
The thing I also notice about clothing during the latter half 18th century, is that exquisite framing of space. Weather it's on a frock coat or a Robe a l'Anglaise. The trim and decoration compliment the simplicity and effortless elegance if the textiles used, rather than to cover it up.
Early 1770s silk brocaded jacquard gown. Self made ruching with fly braid at edge.