“You shouldn’t wear a watch with a tuxedo” is iGent perpetrated nonsense (hot take & mini history lesson)
I occasionally see people say that it’s technically incorrect to wear any watch with a dinner jacket (tuxedo), as it implies you are more concerned with watching the time than having a good time. This may have a grain of historic truth to it but in its modern form it’s complete nonsense.
Back when gentlemen wore white tie for most evening events, they had coachmen to take them home (unless they were staying over at the host’s home). A watch was therefore not necessary and may have signified a preoccupation with watching the time.
However, white tie was only worn by a relatively small portion of the upper classes of society. When black tie (tuxedo) became a more common dress code in the 1920s and 30s, it was worn by a larger strata of society. These did not all have access to their own coachmen or chauffeurs and at the lower end may have needed to rely on public transport to go home. A watch may be a necessity in such circumstances, and since black tie’s rules are less rigid than white tie’s, any custom against watch wearing would not have applied.
So where does that leave you with watches for black tie? Personally I would just say that it should be relatively inconspicuous and subtle. A slim case with a black leather strap does the job best, but the most important thing is that the watch should comfortably fit under your shirt cuff so that it’s not visible unless you are checking the time. Options that fit the bill are available at every price point from a Timex Marlin to a Cartier Tank.