Generally I'd agree that it's a jabot for the Montrose although I have seen it with a white tie (see link and scroll through pic's)
If you look through the galleries for the Royal Caledonian Ball you notice the vast majority wearing jabot and many with cuffs. I had a Sheriffmuir that I did wear with a silk Edwardian style cravat or a riding stock. While the jabot does look good on many, it makes me look like I'm an eye patch and a parrot away from a pirate outfit.....

https://www.tatler.com/gallery/asap-fundraiser