If I can possibly get away with it, I like to wear a small checked shirt with my kilt. In the US, this usually means a button down collar. I draw the line between "dressy " suits and button down collar shirts- they really ought to have a spread collar, especially DB ones. I think a BD is fine for a navy blazer or a tweed jacket. If it is a British ( hacking cut) jacket, I will try for a spread collar, even with a checked shirt. You have to get these shirts from England usually, or from someone who sells the English look... I think bow ties work well with BD collar shirts.

As for the up-or-down collar for black tie, I believe the fashion has gone back and forth. Someone pointed out that tuxedo jackets were originally shortened from tailcoats and thus you wore a wing collar. Through the mid 20th century, the folded down collar ruled. My own worst nightmare is the cheesy wing collar that is often perpetrated- little more than a band with two diminutive points.

As I remember it, the folded down tuxedo collar began slipping in popularity about the time THE STING came out, which showed the 1930s wing collars. Some people link the lapel style to the collar style- shawl lies down, peak gets the wing. Notch lapel is just a bad idea for a tux, sorry. And yes, I read that Prince Philip has one. Too bad for him.