Personally, when the chef takes a lot of trouble presenting his dish, I think it reasonable to dress appropriately; so for me it would still be jacket and tie, and maybe remove the jacket if it was in keeping with other diners. That said, my adult son would be happier in open neck shirt and smart casuals. When going out for a splendid meal, it is better to dress appropriately than dress as if you were visiting a cafe.
Smart Casual is fine
All the above, definitely!
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