Is the nose closest to its future/final shape and size the moment the splint is taken off after surgery?

At time of splint removal, there is a lot of swelling, despite the splint holding some compression beforehand. The tip and supratrip are especially swollen at that time. It just takes time for the swelling to go down. At about 3 months you will see your swelling is 90 to 95% down and at 1 year is the final result.

Sometimes when the splint is removed the nose will appear thinner than it will in its final appearance. This friends on how much pressure is exerted on the nasal splint during healing

Nose appearance upon splint removal: it is partially true that the appearance of the nose when the splint is removed resembles the long-term result. The splint, if it is on rather tight, holds down the swelling, so that when it is removed there is some foretelling of the final appearance. The mid portion of the nose may be slightly thinner than the final outcome if the cast is very tight. Also, the tip may rotate slightly downward with time. The nose then swells and scar tissue builds up underneath the skin, particularly in the tip and supratip area. So the nose often does not look quite as small or thin as it did when the splint was removed. There is then a long slow process of scar tissue resolution which could take 1 to 3 years depending on the thickness of the skin and the thickness of the scar tissue developed. Cortizone injection after a few months can speed up the process. The ultimate long-term appearance of the nose will then be similar to its appearance when the cast was first removed except that the tip might be slightly lower.