To answer just such a question, I put together this little collage showing how different neckwear looks with a Sheriffmuir doublet.

From upper left, going clockwise:
Necktie, solid waistcoat
Necktie, tartan waistcoat
Bowtie, solid waistcoat
Cravat, solid waistcoat
Cravat, tartan waistcoat
Lace Jabot, tartan waistcoat
No neckwear, tartan waistcoat
No neckwear, plain waistcoat

I included those last two just to give a basis for comparion. I don't think I'd ever wear the Sheriffmuir without some kind of neckwear. Of the above, the option I like the least is the bow tie, though that could very well be because I don't like that particular bowtie. This image from Highland Clans shows a velvet sheriffmuir worn with a bow tie that I like the look of much better.


Of course, the classic look is the lace jabot, but if one wanted something more understated, I certainly think the cravat looks nice. I'm actually surprised at how nice the plain neck tie looks, but it certainly dresses it down. I'd recommend it only if one wanted to make the doublet somewhat less formal.