The later ones, 2020 models on, had better trim on the interior, thicker glass, slightly different rear lights, but the biggest under the skin difference was in the suspension/steering. It was modified to incorporate some level of autonomous driving systems, that came in across the whole range of guilias, lane keep assist for steering etc. Apparently steering is not as sharp as the earlier cars. Still better than almost everything else though!
On the 17-20 models the biggest change was after summer 2018, when engines injection system changed to direct and port injection. I believe this was done on the QF to negate the need for extra exhaust filter that the ‘cooking’ model got. All to do with those pesky emission rules.